/**
  * Find model by ID.
  *
  * @param integer|array $id Comment ID
  * @return Comment Model
  * @throws HttpException 404 error if comment not found
  */
 protected function findModel($id)
 {
     /** @var Comment $model */
     $model = Activity::findOne($id);
     if ($model !== null) {
         return $model;
     } else {
         throw new HttpException(404, \Yii::t('net_frenzel_activity', 'FRONTEND_FLASH_RECORD_NOT_FOUND'));
     }
 }