Added explicit nil check in LayoutConstraint
Added explicit nil check in LayoutConstraint

MaWenxing/SnapKit,CoderJackyHuang/SnapKit,ramoslin02/SnapKit,duanhjlt/SnapKit,sandyway/SnapKit,chengkaizone/SnapKit,jiwonsis/SnapKit,JummyHuang/SnapKit,Ju2ender/SnapKit,leasual/SnapKit,loupman/SnapKit,bestwpw/SnapKit,hanangellove/SnapKit,sandyway/SnapKit,sunzeboy/SnapKit,loupman/SnapKit,brittonmobile/SnapKit,cnbin/SnapKit,ernestopino/SnapKit,Rdxer/SnapKit,zht415/SnapKit,dawangjiaowolaixunshan/SnapKit,zilaiyedaren/SnapKit,imjerrybao/SnapKit,msdgwzhy6/SnapKit,zilaiyedaren/SnapKit,sunzeboy/SnapKit,Rdxer/SnapKit,ernestopino/SnapKit,CoderJFCK/SnapKit,ramoslin02/SnapKit,bestwpw/SnapKit,imjerrybao/SnapKit,BlessNeo/SnapKit,dawangjiaowolaixunshan/SnapKit,HackRoy/SnapKit,aleffert/SnapKit,CoderJWYang/SnapKit,duanhjlt/SnapKit,398539445/SnapKit,zhaoguohui/SnapKit,CoderJWYang/SnapKit,zhaoguohui/SnapKit,SnapKit/SnapKit,yujiaao/SnapKit,1yvT0s/SnapKit,zht415/SnapKit,msdgwzhy6/SnapKit,wmfgithub/SnapKit,SnapKit/SnapKit,QuanGe/SnapKit,ArthurKK/SnapKit,Ju2ender/SnapKit,MaWenxing/SnapKit,CoderJackyHuang/SnapKit,pengleelove/SnapKit,brittonmobile/SnapKit,1yvT0s/SnapKit,BlessNeo/SnapKit,pengleelove/SnapKit,sai43/SnapKit,aleffert/SnapKit,sai43/SnapKit,chengkaizone/SnapKit,cnbin/SnapKit,fhchina/SnapKit,HackRoy/SnapKit,lioonline/SnapKit,smalldu/SnapKit,QuanGe/SnapKit,smalldu/SnapKit,fhchina/SnapKit,lioonline/SnapKit,398539445/SnapKit,wmfgithub/SnapKit,jiwonsis/SnapKit,yujiaao/SnapKit,leasual/SnapKit,CoderJFCK/SnapKit,hanangellove/SnapKit,ArthurKK/SnapKit,JummyHuang/SnapKit