/**
  * Removes a topic from a user's list of email subscriptions.
  *
  * @param \tx_mmforum_base $forumObj The plugin object
  * @return string             An error message in case the redirect attempt to
  *                            the previous page fails.
  */
 static function delete(tx_mmforum_base $forumObj)
 {
     $feUserId = intval($GLOBALS['TSFE']->fe_user->user['uid']);
     $topicId = intval($forumObj->piVars['tid']);
     if ($feUserId && $topicId) {
         // Executing database operation
         $this->databaseHandle->exec_DELETEquery('tx_mmforum_topicmail', 'user_id = ' . $feUserId . ' AND topic_id = ' . $topicId . $forumObj->getStoragePIDQuery());
     }
     // Redirecting visitor back to previous page
     $forumObj->redirectToReferrer();
     return $forumObj->pi_getLL('subscr.delSuccess') . '<br />' . $forumObj->pi_getLL('redirect.error') . '<br />';
 }