NUnit +ReSharper raises LoggerException and Last runner error

I am executing an NUnit (3) Test hat creates a Application with MainWindow.
After all my Tests are done i close down the MainWindow via the app.Dispatcher.

which causes the following error:

```sharp

Exit code is 0

Last runner error: Process C:\Program Files (x86)\dotnet\dotnet.exe:46752 exited with code '0'.

--- EXCEPTION #1/1 [LoggerException]
Message = “Process C:\Program Files (x86)\dotnet\dotnet.exe:46752 exited with code '0'.”
ExceptionPath = Root
ClassName = JetBrains.Util.LoggerException
HResult = COR_E_APPLICATION=80131600
StackTraceString = “
 at JetBrains.Util.ILoggerEx.LogMessage(ILogger this, LoggingLevel level, String message) in LogMessage.il:line IL_002E mvid 7C49
    at JetBrains.Util.ILoggerEx.Error(ILogger this, String message) in Error.il:line IL_0000 mvid 7C49
    at JetBrains.ReSharper.UnitTestFramework.Execution.TestRunner.TestRunnerRunStrategy.AnalyseProcessCrash(ProcessExitedUnexpectedlyException ex, IUnitTestRun run) in AnalyseProcessCrash.il:line IL_006B mvid AE94
    at JetBrains.ReSharper.UnitTestFramework.Execution.TestRunner.TestRunnerRunStrategy.Run(IUnitTestRun run) in Run.il:line IL_01C8 mvid AE94
    at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in RunInternal.il:line IL_0040 mvid 477B
    at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext(Thread threadPoolThread) in MoveNext.il:line IL_0000 mvid 477B or MoveNext.il:line IL_0040 mvid 477B
    at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction(IAsyncStateMachineBox box, Boolean allowInlining) in RunOrScheduleAction.il:line IL_003B mvid 477B
    at System.Threading.Tasks.Task.RunContinuations(Object continuationObject) in RunContinuations.il:line IL_0065 mvid 477B or RunContinuations.il:line IL_0090 mvid 477B
    at System.Threading.Tasks.Task.FinishSlow(Boolean userDelegateExecute) in FinishSlow.il:line IL_0003 mvid 477B
    at System.Threading.Tasks.Task.TrySetException(Object exceptionObject) in TrySetException.il:line IL_0022 mvid 477B
    at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.SetException(Exception exception, Task`1& taskField) in SetException.il:line IL_0025 mvid 477B

and so on

```

I need to Close the window, otherwise my Test never finishes.
The exit code '0' indicates that the process finished without errors, so why is this a runner error?

How to resolve this issue?