Master: Return immediately if there are no group sources to hand off
Master: Return immediately if there are no group sources to hand off

In `sendHandoffData`, we weren't properly signalling if we had no group
sources to transfer. This would cause our original process to never exit.

SCPR/StreamMachine,pedropapa/StreamMachine,pteich/StreamMachine,StreamMachine/StreamMachine,pedropapa/StreamMachine,cdgraff/StreamMachine,DreamNetwork/StreamMachine,SCPR/StreamMachine,DreamNetwork/StreamMachine,cdgraff/StreamMachine,StreamMachine/StreamMachine,pteich/StreamMachine