sometimes worker dict has None values. Fixes #276
sometimes worker dict has None values. Fixes #276

ChinaQuants/flower,tellapart/flower,lucius-feng/flower,ucb-bar/bar-crawl-web,ChinaQuants/flower,allengaller/flower,ChinaQuants/flower,Lingling7/flower,getupcloud/flower,pj/flower,alexmojaki/flower,barseghyanartur/flower,jzhou77/flower,jzhou77/flower,alexmojaki/flower,Lingling7/flower,asmodehn/flower,asmodehn/flower,ucb-bar/bar-crawl-web,tellapart/flower,getupcloud/flower,marrybird/flower,asmodehn/flower,getupcloud/flower,pj/flower,lucius-feng/flower,jzhou77/flower,raphaelmerx/flower,marrybird/flower,pygeek/flower,barseghyanartur/flower,barseghyanartur/flower,allengaller/flower,raphaelmerx/flower,Lingling7/flower,allengaller/flower,pj/flower,tellapart/flower,ucb-bar/bar-crawl-web,raphaelmerx/flower,lucius-feng/flower,alexmojaki/flower,pygeek/flower,pygeek/flower,marrybird/flower