WinRT popping modal with Editor results in crash

I have a simple xaml page with an Editor which is displayed as modal.

If I call Navigation.PopModalAsync the app crashes (happens on WinpPhone and Win8.1)

System.NullReferenceException: Object reference not set to an instance of an o
bject.\r\n   at Xamarin.Forms.Platform.WinRT.EditorRenderer.OnLostFocus(Object sender, RoutedEventArgs e)

Any ideas on this?