fix bug

ThinkPHP/Library/Think/Auth.class.php

@@ -152,7 +152,7 @@ class Auth{
             ->table($this->_config['AUTH_GROUP_ACCESS'] . ' a')
             ->where("a.uid='$uid' and g.status='1'")
             ->join($this->_config['AUTH_GROUP']." g on a.group_id=g.id")
-            ->field('rules')->select();
+            ->field('a.rules')->select();
         $groups[$uid]=$user_groups?$user_groups:array();
         return $groups[$uid];
     }