@Nullable
  private GroupTreeNode addFileGroup(FileGroup fileGroup, AbstractTreeNode parent, ActionInfo actionInfo) {
    if (fileGroup.isEmpty()) {
      return null;
    }
    GroupTreeNode group = new GroupTreeNode(actionInfo.getGroupName(fileGroup), fileGroup.getSupportsDeletion(),
                                            fileGroup.getInvalidAttributes(), myProject, fileGroup.getErrorsMap(), fileGroup.getId());
    Disposer.register(this, group);
    parent.add(group);
    for (final String s : fileGroup.getFiles()) {
      group.addFilePath(s);
    }
    return group;
  }
@Nullable
  private GroupTreeNode addFileGroup(FileGroup fileGroup, AbstractTreeNode parent, ActionInfo actionInfo)