修复品牌brand_alif未定义时导致的错误

@@ -313,7 +313,7 @@ class ListProcess
     {
         $fieldArr = array();
         foreach ($array as $k => $v) {
-            $fieldArr[$k] = $v[$field];
+            $fieldArr[$k] = isset($v[$field]) ? $v[$field] : '';
         }
         $sort = $desc == false ? SORT_ASC : SORT_DESC;
         array_multisort($fieldArr, $sort, $array);