macosx: Prevent displaying of end-of-playback view when video track is disabled but playback is ongoing

If the playback end view is enabled and the player is stopped, we want to display the playback end view.

We want to still display the decorative view for audio items.

In other cases, we need to check that the player itself is in a stopped state; removal of the active video on the library window can be triggered by more than just the end of playback (e.g. disabling the video track).

Signed-off-by: Claudio Cambra developer@claudiocambra.com