Nullpointer Exception when using WithLoggerFactory

If I use a separate logger factory with its own ILogger interface implementation for the WithLoggerFactory call, then it is not possible to simply return zero in the implementation of the ILogger.BeginScope function.
This leads to a null pointer exception in TimeLoggerExtensions.Disposable.Dispose, because it is not checked here whether the member variable "Disposable" is set at all.
You can work around this by returning "new CompositeDisposable()" in ILogger.BeginScope, for example.
But you have to know that. This is not recognisable from the error message. I have not found anything about this in the documentation.
My suggestion would be to simply modify the Dispose function:

            public void Dispose()
            {
                _sw.Stop();
                _action(_sw.ElapsedMilliseconds);
                _disposable?.Dispose();
            }

Start by locating TimeLoggerExtensions.Disposable.Dispose and the ILogger.BeginScope implementation used by WithLoggerFactory. Reproduce the null reference with a logger that returns zero from BeginScope, then verify that disposal safely handles the missing disposable without changing the normal logging behavior.