Fixed some minor NPE's that might occur, maybe make an issue if something else happens.

Per-Plot music is here!
/plot set music
/plot toggle music
/plot toggle repeat
permissions:
towny.command.plot.set.music
towny.command.plot.toggle.music
towny.command.plot.toggle.repeat

there might be some issues since this is a bit of a rework/rewrite on how players enter and get music on towns

- Fixed Fading out every other music that isn't by this plugin when leaving a town.

Fixed /ta set music not working
if 1.16-1.17 support doesn't work please make an issue in github!

should fix an NPE for existing towns