private void pack() {
    if (branchDummy == null) return;

    if (request != null) {
      Object param = request.getParameter(MindMapUI.PARAM_PROPERTY_PREFIX + Core.StructureClass);
      if (param instanceof String) {
        branchDummy.getTopic().setStructureClass((String) param);
      }
    }
    branchDummy.pack();
  }