public static function getValidFileTypesForCategory()
  {
    $db = \Database::getInstance();
    $input = \Input::getInstance();
    if($db->tableExists('tl_dms_categories') && $db->tableExists('tl_dms_documents'))
    {
      $objCategory = $db->prepare('SELECT cat.* FROM tl_dms_categories cat JOIN tl_dms_documents doc ON doc.pid = cat.id WHERE doc.id = ?')->execute($input->get('id'));
      if ($objCategory->numRows)
      {
        return $objCategory->file_types;
      }
    }
    return "";
  }