oddb/pq: allow device without user id to be saved
oddb/pq: allow device without user id to be saved

rickmak/skygear-server,SkygearIO/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server,SkygearIO/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server