Do not automatically reopen Music when quit

[FloatingMilkshake]

It would be nice if, when Music is quit, Ongaku could hang around in the background without reopening it, waiting for the next time it's manually reopened!

[slice]

IIRC this happens because Ongaku is repeatedly querying for the player state via AppleScript, which automatically launches the app if it's closed—it doesn't check if Music is open or not before doing so.