clicking on the specific clip in the timeline. Undo/Redo in effects is done, but doesn't appear right away. You have to re-click on the clip in the timeline, to see that it was undone/redone.
crashes with this "app" argument non-coherency
for medialibrary. Undo for effect takes place but not immediately (after clicking again on the clip), for the moment.
Stop playback when reaching the end of the timeline
Doing simply "return" returns None anyway.
This prevents a traceback when resizing the main window