Fix a KVO-related crash
Fix a KVO-related crash

If we invoke setupPlayerItem: with a non-nil playerItem, self.playerItem would be deallocated, and the removeObserver stuff were not invoked.

i17c/Player,xhacker/Player,piemonte/Player,piemonte/Player,lumenlunae/Player,lumenlunae/Player,pgherveou/Player,Flyreel/Player,Flyreel/Player,ppamorim/Player,ppamorim/Player,pgherveou/Player,i17c/Player,piemonte/Player,xhacker/Player,lumenlunae/Player