From ba6132715c356e5fd35f38747bb4477bec132863 Mon Sep 17 00:00:00 2001
From: Garry Newman <garrynewman@users.noreply.github.com>
Date: Wed, 31 Jan 2018 11:40:58 +0000
Subject: [PATCH] Don't try to make callback with invalid SteamAPICall_t

---
 .../SteamNative/SteamNative.SteamApps.cs      |  1 +
 .../SteamNative/SteamNative.SteamFriends.cs   |  6 ++++++
 .../SteamNative.SteamGameServer.cs            |  3 +++
 .../SteamNative.SteamGameServerStats.cs       |  2 ++
 .../SteamNative.SteamHTMLSurface.cs           |  1 +
 .../SteamNative/SteamNative.SteamInventory.cs |  3 +++
 .../SteamNative.SteamMatchmaking.cs           |  3 +++
 .../SteamNative.SteamRemoteStorage.cs         | 21 +++++++++++++++++++
 .../SteamNative/SteamNative.SteamUGC.cs       | 18 ++++++++++++++++
 .../SteamNative/SteamNative.SteamUser.cs      |  2 ++
 .../SteamNative/SteamNative.SteamUserStats.cs | 10 +++++++++
 .../SteamNative/SteamNative.SteamUtils.cs     |  1 +
 Generator/CodeWriter/Class.cs                 |  1 +
 13 files changed, 72 insertions(+)

diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamApps.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamApps.cs
index 61114d5..2f28d3c 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamApps.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamApps.cs
@@ -184,6 +184,7 @@ namespace SteamNative
 			callback = platform.ISteamApps_GetFileDetails( pszFileName );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return FileDetailsResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamFriends.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamFriends.cs
index 822fb33..6734548 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamFriends.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamFriends.cs
@@ -98,6 +98,7 @@ namespace SteamNative
 			callback = platform.ISteamFriends_EnumerateFollowingList( unStartIndex );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return FriendsEnumerateFollowingList_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -193,6 +194,7 @@ namespace SteamNative
 			callback = platform.ISteamFriends_GetFollowerCount( steamID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return FriendsGetFollowerCount_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -429,6 +431,7 @@ namespace SteamNative
 			callback = platform.ISteamFriends_IsFollowing( steamID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return FriendsIsFollowing_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -446,6 +449,7 @@ namespace SteamNative
 			callback = platform.ISteamFriends_JoinClanChatRoom( steamIDClan.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return JoinClanChatRoomCompletionResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -475,6 +479,7 @@ namespace SteamNative
 			callback = platform.ISteamFriends_RequestClanOfficerList( steamIDClan.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return ClanOfficerListResponse_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -516,6 +521,7 @@ namespace SteamNative
 			callback = platform.ISteamFriends_SetPersonaName( pchPersonaName );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SetPersonaNameResponse_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServer.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServer.cs
index 507141f..bc8d46a 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServer.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServer.cs
@@ -50,6 +50,7 @@ namespace SteamNative
 			callback = platform.ISteamGameServer_AssociateWithClan( steamIDClan.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return AssociateWithClanResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -97,6 +98,7 @@ namespace SteamNative
 			callback = platform.ISteamGameServer_ComputeNewPlayerCompatibility( steamIDNewPlayer.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return ComputeNewPlayerCompatibilityResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -156,6 +158,7 @@ namespace SteamNative
 			callback = platform.ISteamGameServer_GetServerReputation();
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GSReputation_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServerStats.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServerStats.cs
index 14cb187..706408c 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServerStats.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamGameServerStats.cs
@@ -74,6 +74,7 @@ namespace SteamNative
 			callback = platform.ISteamGameServerStats_RequestUserStats( steamIDUser.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GSStatsReceived_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -103,6 +104,7 @@ namespace SteamNative
 			callback = platform.ISteamGameServerStats_StoreUserStats( steamIDUser.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GSStatsStored_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamHTMLSurface.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamHTMLSurface.cs
index 1d6b917..3f434bb 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamHTMLSurface.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamHTMLSurface.cs
@@ -68,6 +68,7 @@ namespace SteamNative
 			callback = platform.ISteamHTMLSurface_CreateBrowser( pchUserAgent, pchUserCSS );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return HTML_BrowserReady_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamInventory.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamInventory.cs
index 75da1b4..d6de777 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamInventory.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamInventory.cs
@@ -243,6 +243,7 @@ namespace SteamNative
 			callback = platform.ISteamInventory_RequestEligiblePromoItemDefinitionsIDs( steamID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SteamInventoryEligiblePromoItemDefIDs_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -254,6 +255,7 @@ namespace SteamNative
 			callback = platform.ISteamInventory_RequestPrices();
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SteamInventoryRequestPricesResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -301,6 +303,7 @@ namespace SteamNative
 			callback = platform.ISteamInventory_StartPurchase( pArrayItemDefs.Select( x => x.Value ).ToArray(), punArrayQuantity, unArrayLength );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SteamInventoryStartPurchaseResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamMatchmaking.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamMatchmaking.cs
index 97c80e2..da740fe 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamMatchmaking.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamMatchmaking.cs
@@ -98,6 +98,7 @@ namespace SteamNative
 			callback = platform.ISteamMatchmaking_CreateLobby( eLobbyType, cMaxMembers );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LobbyCreated_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -219,6 +220,7 @@ namespace SteamNative
 			callback = platform.ISteamMatchmaking_JoinLobby( steamIDLobby.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LobbyEnter_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -248,6 +250,7 @@ namespace SteamNative
 			callback = platform.ISteamMatchmaking_RequestLobbyList();
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LobbyMatchList_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamRemoteStorage.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamRemoteStorage.cs
index 8493623..22de4be 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamRemoteStorage.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamRemoteStorage.cs
@@ -50,6 +50,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_CommitPublishedFileUpdate( updateHandle.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageUpdatePublishedFileResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -67,6 +68,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_DeletePublishedFile( unPublishedFileId.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageDeletePublishedFileResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -78,6 +80,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_EnumeratePublishedFilesByUserAction( eAction, unStartIndex );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageEnumeratePublishedFilesByUserActionResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -115,6 +118,7 @@ namespace SteamNative
 			}
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageEnumerateWorkshopFilesResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -126,6 +130,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_EnumerateUserPublishedFiles( unStartIndex );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageEnumerateUserPublishedFilesResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -163,6 +168,7 @@ namespace SteamNative
 			}
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageEnumerateUserPublishedFilesResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -174,6 +180,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_EnumerateUserSubscribedFiles( unStartIndex );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageEnumerateUserSubscribedFilesResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -215,6 +222,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_FileReadAsync( pchFile, nOffset, cubToRead );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageFileReadAsyncComplete_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -232,6 +240,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_FileShare( pchFile );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageFileShareResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -249,6 +258,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_FileWriteAsync( pchFile, (IntPtr) pvData, cubData );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageFileWriteAsyncComplete_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -323,6 +333,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_GetPublishedFileDetails( unPublishedFileId.Value, unMaxSecondsOld );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageGetPublishedFileDetailsResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -334,6 +345,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_GetPublishedItemVoteDetails( unPublishedFileId.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageGetPublishedItemVoteDetailsResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -377,6 +389,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_GetUserPublishedItemVoteDetails( unPublishedFileId.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageGetPublishedItemVoteDetailsResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -426,6 +439,7 @@ namespace SteamNative
 			}
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStoragePublishFileProgress_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -463,6 +477,7 @@ namespace SteamNative
 			}
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStoragePublishFileProgress_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -486,6 +501,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_SetUserPublishedFileAction( unPublishedFileId.Value, eAction );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageSetUserPublishedFileActionResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -497,6 +513,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_SubscribePublishedFile( unPublishedFileId.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageSubscribePublishedFileResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -508,6 +525,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_UGCDownload( hContent.Value, unPriority );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageDownloadUGCResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -519,6 +537,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_UGCDownloadToLocation( hContent.Value, pchLocation, unPriority );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageDownloadUGCResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -536,6 +555,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_UnsubscribePublishedFile( unPublishedFileId.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageUnsubscribePublishedFileResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -615,6 +635,7 @@ namespace SteamNative
 			callback = platform.ISteamRemoteStorage_UpdateUserPublishedItemVote( unPublishedFileId.Value, bVoteUp );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageUpdateUserPublishedItemVoteResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUGC.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUGC.cs
index 7d6edf9..eb9dad7 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUGC.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUGC.cs
@@ -50,6 +50,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_AddAppDependency( nPublishedFileID.Value, nAppID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return AddAppDependencyResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -61,6 +62,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_AddDependency( nParentPublishedFileID.Value, nChildPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return AddUGCDependencyResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -96,6 +98,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_AddItemToFavorites( nAppId.Value, nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return UserFavoriteItemsListChanged_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -125,6 +128,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_CreateItem( nConsumerAppId.Value, eFileType );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return CreateItemResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -159,6 +163,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_DeleteItem( nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return DeleteItemResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -176,6 +181,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_GetAppDependencies( nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GetAppDependenciesResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -329,6 +335,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_GetUserItemVote( nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GetUserItemVoteResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -346,6 +353,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_RemoveAppDependency( nPublishedFileID.Value, nAppID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoveAppDependencyResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -357,6 +365,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_RemoveDependency( nParentPublishedFileID.Value, nChildPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoveUGCDependencyResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -368,6 +377,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_RemoveItemFromFavorites( nAppId.Value, nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return UserFavoriteItemsListChanged_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -397,6 +407,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_SendQueryUGCRequest( handle.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SteamUGCQueryCompleted_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -566,6 +577,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_SetUserItemVote( nPublishedFileID.Value, bVoteUp );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SetUserItemVoteResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -588,6 +600,7 @@ namespace SteamNative
 			}
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return StartPlaytimeTrackingResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -604,6 +617,7 @@ namespace SteamNative
 			}
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return StopPlaytimeTrackingResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -615,6 +629,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_StopPlaytimeTrackingForAllItems();
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return StopPlaytimeTrackingResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -626,6 +641,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_SubmitItemUpdate( handle.Value, pchChangeNote );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return SubmitItemUpdateResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -637,6 +653,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_SubscribeItem( nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageSubscribePublishedFileResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -654,6 +671,7 @@ namespace SteamNative
 			callback = platform.ISteamUGC_UnsubscribeItem( nPublishedFileID.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return RemoteStorageUnsubscribePublishedFileResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUser.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUser.cs
index 91d8b4e..443cee6 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUser.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUser.cs
@@ -188,6 +188,7 @@ namespace SteamNative
 			callback = platform.ISteamUser_RequestEncryptedAppTicket( (IntPtr) pDataToInclude, cbDataToInclude );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return EncryptedAppTicketResponse_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -199,6 +200,7 @@ namespace SteamNative
 			callback = platform.ISteamUser_RequestStoreAuthURL( pchRedirectURL );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return StoreAuthURLResponse_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUserStats.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUserStats.cs
index 201a82b..c7c3e16 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUserStats.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUserStats.cs
@@ -50,6 +50,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_AttachLeaderboardUGC( hSteamLeaderboard.Value, hUGC.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LeaderboardUGCSet_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -67,6 +68,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_DownloadLeaderboardEntries( hSteamLeaderboard.Value, eLeaderboardDataRequest, nRangeStart, nRangeEnd );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LeaderboardScoresDownloaded_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -78,6 +80,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_DownloadLeaderboardEntriesForUsers( hSteamLeaderboard.Value, (IntPtr) prgUsers, cUsers );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LeaderboardScoresDownloaded_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -89,6 +92,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_FindLeaderboard( pchLeaderboardName );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LeaderboardFindResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -100,6 +104,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_FindOrCreateLeaderboard( pchLeaderboardName, eLeaderboardSortMethod, eLeaderboardDisplayType );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LeaderboardFindResult_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -244,6 +249,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_GetNumberOfCurrentPlayers();
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return NumberOfCurrentPlayers_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -303,6 +309,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_RequestGlobalAchievementPercentages();
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GlobalAchievementPercentagesReady_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -314,6 +321,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_RequestGlobalStats( nHistoryDays );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return GlobalStatsReceived_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -325,6 +333,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_RequestUserStats( steamIDUser.Value );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return UserStatsReceived_t.CallResult( steamworks, callback, CallbackFunction );
 		}
@@ -372,6 +381,7 @@ namespace SteamNative
 			callback = platform.ISteamUserStats_UploadLeaderboardScore( hSteamLeaderboard.Value, eLeaderboardUploadScoreMethod, nScore, pScoreDetails, cScoreDetailsCount );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return LeaderboardScoreUploaded_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUtils.cs b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUtils.cs
index 76f224d..dec7642 100644
--- a/Facepunch.Steamworks/SteamNative/SteamNative.SteamUtils.cs
+++ b/Facepunch.Steamworks/SteamNative/SteamNative.SteamUtils.cs
@@ -56,6 +56,7 @@ namespace SteamNative
 			callback = platform.ISteamUtils_CheckFileSignature( szFileName );
 			
 			if ( CallbackFunction == null ) return null;
+			if ( callback == 0 ) return null;
 			
 			return CheckFileSignature_t.CallResult( steamworks, callback, CallbackFunction );
 		}
diff --git a/Generator/CodeWriter/Class.cs b/Generator/CodeWriter/Class.cs
index df76dbc..896a5fd 100644
--- a/Generator/CodeWriter/Class.cs
+++ b/Generator/CodeWriter/Class.cs
@@ -175,6 +175,7 @@ namespace Generator
 
             AfterLines.Add( "" );
             AfterLines.Add( "if ( CallbackFunction == null ) return null;" );
+            AfterLines.Add("if ( callback == 0 ) return null;");
             AfterLines.Add( "" );
 
             AfterLines.Add( $"return {MethodDef.CallResult}.CallResult( steamworks, callback, CallbackFunction );" );