Since we don't get a mozfullscreenchange event anymore, I think you have to call hidePlayer() here, don't you?  If we delete the playing video and remain in player mode, there won't be anything to display.

Ideally, though we would only leave the player mode if the user confirmed the deletion. If they cancel it, we should probably stay in player mode.  But that would require refactoring other code, and is a different bug, so I suggest you just add hidePlayer() here.