OpenFileDialog crashes program

When canceling on OpenFileDialog on linux the application crashes. Steps to reproduce:

1. Open OpenFileDialog
2. Press Cancel

expected behavior: the application does not crash behavior: the application crashes

Exception

Unhandled exception. ReactiveUI.UnhandledErrorException: An object implementing IHandleObservableErrors (often a ReactiveCommand or ObservableAsPropertyHelper) has errored, thereby breaking its observable pipeline. To prevent this, ensure the pipeline does not error, or Subscribe to the ThrownExceptions property of the object in question to handle the erroneous case. ---> System.ArgumentNullException: Value cannot be null. (Parameter 'source') at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument) at System.Linq.Enumerable.TryGetFirst[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found) at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) at FrameTimeHandler.ViewModels.MainWindowViewModel.<.ctor>b__94_0() --- End of inner exception stack trace --- at ReactiveUI.RxApp.<>c__DisplayClass9_0.<.cctor>b__2() in d:\a\1\s\src\ReactiveUI\RxApp.cs:line 103 at System.Reactive.Concurrency.Scheduler.Invoke(IScheduler scheduler, Action action) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Concurrency\Scheduler.Simple.cs:line 254 at System.Reactive.Concurrency.Scheduler.<>c.<Schedule>b__74_0(IScheduler s, Action a) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Concurrency\Scheduler.Simple.cs:line 37 at Avalonia.Threading.AvaloniaScheduler.Schedule[TState](TState state, TimeSpan dueTime, Func`3 action) at System.Reactive.Concurrency.LocalScheduler.Schedule[TState](TState state, Func`3 action) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Concurrency\LocalScheduler.cs:line 32 at System.Reactive.Concurrency.Scheduler.Schedule(IScheduler scheduler, Action action) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Concurrency\Scheduler.Simple.cs:line 37 at ReactiveUI.RxApp.<>c.<.cctor>b__9_1(Exception ex) in d:\a\1\s\src\ReactiveUI\RxApp.cs:line 108 at System.Reactive.AnonymousSafeObserver`1.OnNext(T value) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\AnonymousSafeObserver.cs:line 44 at System.Reactive.ObserveOnObserverNew`1.DrainStep(ConcurrentQueue`1 q) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Internal\ScheduledObserver.cs:line 577 at System.Reactive.ObserveOnObserverNew`1.DrainShortRunning(IScheduler recursiveScheduler) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Internal\ScheduledObserver.cs:line 509 at System.Reactive.ObserveOnObserverNew`1.<>c.<.cctor>b__17_0(IScheduler scheduler, ObserveOnObserverNew`1 self) in D:\a\1\s\Rx.NET\Source\src\System.Reactive\Internal\ScheduledObserver.cs:line 497 at Avalonia.Threading.AvaloniaScheduler.<>c__DisplayClass2_1`1.<Schedule>b__1() at Avalonia.Threading.JobRunner.Job.Avalonia.Threading.JobRunner.IJob.Run() at Avalonia.Threading.JobRunner.RunJobs(Nullable`1 priority) at Avalonia.X11.X11PlatformThreading.CheckSignaled() at Avalonia.X11.X11PlatformThreading.RunLoop(CancellationToken cancellationToken) at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken) at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args) at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode) at FrameTimeHandler.Program.Main(String[] args)

[localcc]

DotNet Core 3.1.301 Avalonia version: 0.9.11 OS: Ubuntu 19.04 64bit Build configurations tried: both release and debug Source code link: https://github.com/FlexxxerAlex/frametime-handler

[kekekeks]

The null check is there

No, it is not: https://github.com/FlexxxerAlex/frametime-handler/blob/master/FrameTimeHandler/ViewModels/MainWindowViewModel.cs#L285-L287