Avalonia: Adding/Removing classes in codebehind crashes on PriorityLevel.cs

[jmacato]

try out RenderDemo on https://github.com/AvaloniaUI/Avalonia/tree/repro-bindingprio-bug and repeatedly click the Pause/Resume Animations button.

cc: @MarchingCube

I tried fixing it by adding the following check on PriorityLevel.cs and it seem to work but im not sure if that's the correct fix.

Line 204:

                    if (_bindings.Count > 0)
                        _bindings.Remove(_binding);

[MarchingCube]

Looks like we are unsubscribing twice, will investigate.

[MarchingCube]

Fixed in https://github.com/AvaloniaUI/Avalonia/pull/3062.