Clear up use_null logic
Clear up use_null logic

zhaozg/luvit,sousoux/luvit,bsn069/luvit,rjeli/luvit,boundary/luvit,AndrewTsao/luvit,DBarney/luvit,AndrewTsao/luvit,GabrielNicolasAvellaneda/luvit-upstream,sousoux/luvit,connectFree/lev,rjeli/luvit,boundary/luvit,boundary/luvit,GabrielNicolasAvellaneda/luvit-upstream,DBarney/luvit,luvit/luvit,boundary/luvit,zhaozg/luvit,boundary/luvit,boundary/luvit,luvit/luvit,GabrielNicolasAvellaneda/luvit-upstream,sousoux/luvit,rjeli/luvit,AndrewTsao/luvit,DBarney/luvit,sousoux/luvit,GabrielNicolasAvellaneda/luvit-upstream,sousoux/luvit,rjeli/luvit,DBarney/luvit,kaustavha/luvit,sousoux/luvit,bsn069/luvit,connectFree/lev,bsn069/luvit,kaustavha/luvit,kaustavha/luvit