another fix for linearizeAll and undefined lins

src/runtime/c/pgf/linearizer.cxx

@@ -419,7 +419,7 @@ bool PgfLinearizer::TreeLinrefNode::resolve(PgfLinearizer *linearizer)
     TreeNode *root = args;
     ref<PgfConcrLincat> lincat = root->get_lincat(linearizer);
     if (lincat == 0)
-        return true;
+        return (lin_index = !lin_index);
 
     while (lincat->n_lindefs+lin_index < lincat->res->len) {
         // Unbind all variables