small change to allow stop <- false

[korvyr]

This will allow for a little select{} magic to check if something is still playing without killing the current playback:

select{
case stop <- false:
   // still alive and didn't kill
case stop <- true:
   // was alive, but just killed
default:
   // was already dead
}

[korvyr]

This seemed to cause some unknown issues with the stream not wanting to stop at all even when requested.