lib/sync: Cleanly fail instead of panic in tests (#6088)
lib/sync: Cleanly fail instead of panic in tests (#6088)


wweich/syncthing,syncthing/syncthing,syncthing/syncthing,wweich/syncthing,syncthing/syncthing,AudriusButkevicius/syncthing,AudriusButkevicius/syncthing,AudriusButkevicius/syncthing,syncthing/syncthing,syncthing/syncthing,AudriusButkevicius/syncthing,imsodin/syncthing,wweich/syncthing,wweich/syncthing,imsodin/syncthing,imsodin/syncthing,imsodin/syncthing,imsodin/syncthing,syncthing/syncthing