oops, typo

panda/src/pgraph/sceneGraphReducer.cxx

@@ -755,7 +755,7 @@ do_flatten_siblings(PandaNode *parent_node, PandaNode *child1,
   // Make sure the new child list has child1's children first,
   // followed by child2's children.
   child1->replace_node(child2);
-  new_child->replace_node(child2);
+  new_child->replace_node(child1);
 
   return new_child;
 }