[-] BO: Fix SQL error on click on notification if no new notifications

classes/Notification.php

@@ -148,7 +148,7 @@ class NotificationCore
 			return Db::getInstance()->execute('
 					UPDATE `'._DB_PREFIX_.'employee`
 					SET `id_last_'.bqSQL($type).'` = (
-						SELECT MAX(`id_'.$type.'`)
+						SELECT IFNULL(MAX(`id_'.$type.'`), 0)
 						FROM `'._DB_PREFIX_.(($type == 'order') ? bqSQL($type).'s' : bqSQL($type)).'`
 					)
 					WHERE `id_employee` = '.(int)$cookie->id_employee);