[fix] Ensure err.stack exists before splitting it. Fixes #152
[fix] Ensure err.stack exists before splitting it. Fixes #152

unlucio/winston,paulhroth/winston,modulexcite/winston,rakesh-mohanta/winston,SmartNode-es/winston,nikolas/winston,pantheon-systems/winston,s-panferov/winston,winstonjs/winston,wancharle/winston,beni55/winston,get-trucked/winston,dustinblackman/winston,z-10/winston,dbmikus/winston,uber/winston,whismat/winston,tobli/winston,winstonjs/winston,jjmleiro/winston,megastef/winston,auth0/winston,apiaryio/winston,alinex/winston,aquavitae/winston,thaliproject/winston,psquickitjayant/winston,alphagov/winston,harriha/winston,DenisGorbachev/winston