nak3: Allow empty string for Group field to indicate core API group

JobBuild
562
07-27 01:43
pull-gateway-api-test 1419880270709919744 1419878899147345920 1419836483283456000 1419835783845515264
pull-gateway-api-verify 1419880270676365312 1419878899117985792 1419836483249901568 1419835783811960832