Fix null pointer error in type checker when tuple type contains null type
Fix null pointer error in type checker when tuple type contains null type

andrewkatis/jkind-1,lgwagner/jkind,lgwagner/jkind,agacek/jkind,backesj/jkind,agacek/jkind,backesj/jkind,andrewkatis/jkind-1