vm.c: initialize line always

* vm.c (rb_source_location): reset line to 0 if no location is
  found.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52397 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

vm.c

@@ -1124,6 +1124,7 @@ rb_source_location(int *pline)
 	return cfp->iseq->body->location.path;
     }
     else {
+	if (pline) *pline = 0;
 	return 0;
     }
 }