SDLUI vsid should not stop playing on menu invocation.
As noted in bug #452, at this time it is not possible to assign hot keys to
emulator actions. When one invokes the menu to for example change the SID type
or play another sub tune the emulation stops playing which is very annoying.
Probably the menu rendering could be made independent from the VIC2 rendering,
which supposedly is not needed anyway (though it looks very nice with songs in