Can't cook game in 4.21

Hi!

I can build all configurations except the ‘Shipping’ configuration. I use Visual Studio 2017 (Version 15.9.2).

The error is the following:

2>UnrealBuildTool : error : System.NullReferenceException: Object reference not set to an instance of an object.
2>                           at UnrealBuildTool.UEBuildBinary.<>c.<SetupBinaryLinkEnvironment>b__37_1(FileItem Item) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 752
2>                           at System.Linq.Enumerable.WhereSelectListIterator`2.MoveNext()
2>                           at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)
2>                           at UnrealBuildTool.UEBuildBinary.SetupBinaryLinkEnvironment(ReadOnlyTargetRules Target, UEToolChain ToolChain, LinkEnvironment LinkEnvironment, CppCompileEnvironment CompileEnvironment, List`1 SharedPCHs, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, ActionGraph ActionGraph) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 752
2>                           at UnrealBuildTool.UEBuildBinary.Build(ReadOnlyTargetRules Target, UEToolChain ToolChain, CppCompileEnvironment CompileEnvironment, LinkEnvironment LinkEnvironment, List`1 SharedPCHs, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, ActionGraph ActionGraph) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 193
2>                           at UnrealBuildTool.UEBuildTarget.Build(BuildConfiguration BuildConfiguration, CPPHeaders Headers, List`1 OutputItems, List`1 UObjectModules, ISourceFileWorkingSet WorkingSet, ActionGraph ActionGraph, EHotReload HotReload, Boolean bIsAssemblingBuild) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildTarget.cs:line 2193
2>                           at UnrealBuildTool.UnrealBuildTool.RunUBT(BuildConfiguration BuildConfiguration, String[] Arguments, FileReference ProjectFile, Boolean bCatchExceptions) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.cs:line 1503
2>                        (see ../Programs/UnrealBuildTool/Log.txt for full exception trace)

The log shows the following error:

ExternalExecution.ExecuteHeaderToolIfNecessary: Reflection code generated for RTSGame in 18.7816805 seconds
Log.WriteException: ==============================================================================
Log.WriteException: ERROR: System.NullReferenceException: Object reference not set to an instance of an object.
Log.WriteException:           at UnrealBuildTool.UEBuildBinary.<>c.<SetupBinaryLinkEnvironment>b__37_1(FileItem Item) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 752
Log.WriteException:           at System.Linq.Enumerable.WhereSelectListIterator`2.MoveNext()
Log.WriteException:           at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)
Log.WriteException:           at UnrealBuildTool.UEBuildBinary.SetupBinaryLinkEnvironment(ReadOnlyTargetRules Target, UEToolChain ToolChain, LinkEnvironment LinkEnvironment, CppCompileEnvironment CompileEnvironment, List`1 SharedPCHs, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, ActionGraph ActionGraph) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 752
Log.WriteException:           at UnrealBuildTool.UEBuildBinary.Build(ReadOnlyTargetRules Target, UEToolChain ToolChain, CppCompileEnvironment CompileEnvironment, LinkEnvironment LinkEnvironment, List`1 SharedPCHs, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, ActionGraph ActionGraph) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 193
Log.WriteException:           at UnrealBuildTool.UEBuildTarget.Build(BuildConfiguration BuildConfiguration, CPPHeaders Headers, List`1 OutputItems, List`1 UObjectModules, ISourceFileWorkingSet WorkingSet, ActionGraph ActionGraph, EHotReload HotReload, Boolean bIsAssemblingBuild) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildTarget.cs:line 2193
Log.WriteException:           at UnrealBuildTool.UnrealBuildTool.RunUBT(BuildConfiguration BuildConfiguration, String[] Arguments, FileReference ProjectFile, Boolean bCatchExceptions) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.cs:line 1503
Log.WriteException:        (see C:\Users\Stoffe\AppData\Roaming\Unreal Engine\AutomationTool\Logs\C+Program+Files+Epic+Games+UE_4.21\UBT-RTSGame-Win64-Shipping_2.txt for full exception trace)
Log.WriteException: 
Log.WriteException: NullReferenceException: Object reference not set to an instance of an object.
Log.WriteException:    at UnrealBuildTool.UEBuildBinary.<>c.<SetupBinaryLinkEnvironment>b__37_1(FileItem Item) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 752
Log.WriteException:    at System.Linq.Enumerable.WhereSelectListIterator`2.MoveNext()
Log.WriteException:    at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)
Log.WriteException:    at UnrealBuildTool.UEBuildBinary.SetupBinaryLinkEnvironment(ReadOnlyTargetRules Target, UEToolChain ToolChain, LinkEnvironment LinkEnvironment, CppCompileEnvironment CompileEnvironment, List`1 SharedPCHs, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, ActionGraph ActionGraph) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 752
Log.WriteException:    at UnrealBuildTool.UEBuildBinary.Build(ReadOnlyTargetRules Target, UEToolChain ToolChain, CppCompileEnvironment CompileEnvironment, LinkEnvironment LinkEnvironment, List`1 SharedPCHs, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, ActionGraph ActionGraph) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildBinary.cs:line 193
Log.WriteException:    at UnrealBuildTool.UEBuildTarget.Build(BuildConfiguration BuildConfiguration, CPPHeaders Headers, List`1 OutputItems, List`1 UObjectModules, ISourceFileWorkingSet WorkingSet, ActionGraph ActionGraph, EHotReload HotReload, Boolean bIsAssemblingBuild) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildTarget.cs:line 2193
Log.WriteException:    at UnrealBuildTool.UnrealBuildTool.RunUBT(BuildConfiguration BuildConfiguration, String[] Arguments, FileReference ProjectFile, Boolean bCatchExceptions) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.cs:line 1503
Log.WriteException: ==============================================================================

Any ideas what may be causing this issue? This problem blocks us from upgrading to 4.21. The editor works as expected.

Thanks in advance!

This problem seems to be related to a plugin we used. When removed, the game cooks as expected.