Fix case of invalid user email
Fix case of invalid user email

If the user email was set improperly (in this case it was sent as just '@'), string split returns a null or 0 length array, which we then index improperly.

MarkEWaite/git-plugin,jenkinsci/git-plugin,martinda/git-plugin,jenkinsci/git-plugin,recena/git-plugin,ndeloof/git-plugin,mklein0/git-plugin,mklein0/git-plugin,ndeloof/git-plugin,martinda/git-plugin,MarkEWaite/git-plugin,kzantow/git-plugin,jenkinsci/git-plugin,MarkEWaite/git-plugin,recena/git-plugin,v1v/git-plugin,martinda/git-plugin,recena/git-plugin,MarkEWaite/git-plugin,mklein0/git-plugin,v1v/git-plugin,jenkinsci/git-plugin,jacob-keller/git-plugin,ndeloof/git-plugin,kzantow/git-plugin,jacob-keller/git-plugin,jacob-keller/git-plugin,v1v/git-plugin,kzantow/git-plugin