填写邀请人

application/api/controller/User.php

@@ -139,7 +139,7 @@ class User extends Api
         }
         $user_id = $this->auth->id;
 
-        if(!empty($this->auth->pre_userid)){
+        if($this->auth->pre_userid){
             $this->error('您已经填写过邀请人');
         }