public function performDeleteTopic()
 {
     if (!count($_POST['topic_id'])) {
         ilUtil::sendInfo($this->lng->txt('select_one_topic'));
     } else {
         foreach ($_POST['topic_id'] as $topic_id) {
             $oTopic = new ilShopTopic($topic_id);
             $oTopic->delete();
             unset($oTopic);
         }
         ilUtil::sendInfo($this->lng->txt('topics_deleted'));
     }
     $this->showTopicsList();
     return true;
 }