private @Nullable NodeContent getRootContent(@NotNull Obsolescent obsolescent) {
    assert invoker != null ? invoker.isValidThread() : EventQueue.isDispatchThread();
    if (obsolescent.isObsolete()) return null;
    Object root = model.getRoot();
    if (root == null || obsolescent.isObsolete()) return null;
    return new NodeContent(root, LeafState.get(root, model));
  }
private @Nullable NodeContent getRootContent(@NotNull Obsolescent obsolescent)