@Nullable
  private FragmentNode getFirstSelectedNode() {
    TreePath[] selectionPaths = myTree.getSelectionPaths();
    if (ArrayUtil.isEmpty(selectionPaths)) {
      return null;
    }
    for (TreePath path : selectionPaths) {
      List<FragmentNode> nodes = getFragmentNodes(path);
      if (!nodes.isEmpty()) {
        return nodes.get(0);
      }
    }
    return null;
  }
@Nullable
  private FragmentNode getFirstSelectedNode()