message: Update addChildOfCategory for root-level node elements in v1.36
diff: @@ -277,7 +277,7 @@ ElementPtr Element::addChildOfCategory(const string& category,
  }
  // Check for a node within a graph.
  - if (!child && getCategory() == NodeGraph::CATEGORY)
  + if (!child && isA<GraphElement>())
  {
  child = createElement<Node>(getSelf(), childName);
  child->setCategory(category);
  