Music widget does some polling even if muted

[sprunk]

There is some sort of polling every 0.03s going on regardless of whether music is muted. Doesn't seem to do much harm other than waste a bit of perf but maybe there's other mistaken assumptions to uncover? https://github.com/ZeroK-RTS/Zero-K/blob/b9f90e01c99739f81c02fc36254e7d53e20ed85f/LuaUI/Widgets/snd_music2.lua#L336-L339