don't try to sync with empty event list
don't try to sync with empty event list

unnecessary and breaks on some servers (e.g., fruux)

dzoep/khal,sheeprine/khal,sithglan/khal,hobarrera/khal,sheeprine/khal,pdav/khal,pimutils/khal,sdx23/khal,geier/khal,sithglan/khal