完善跟新用户三方信息方法

app/controller/api/user/User.php

@@ -2654,9 +2654,9 @@ class User extends BaseController
                 $data = ["wechat_user_id" => $openid];
                 $unionId = $openid;
                 $existUid = Db::name('user_extract_openid')->where('openid',$unionId)->value('uid');
-                if ($existUid != $uid) throw new \Exception("此微信号已被绑定");
+                if (!empty($existUid) && $existUid != $uid) throw new \Exception("此微信号已被绑定");
                 $check = Db::name('user_extract_openid')->where('uid',$uid)->value('openid');
-                if ($check != $unionId) throw new \Exception("当前用户已绑定其他微信号");
+                if (!empty($check) && $check != $unionId) throw new \Exception("当前用户已绑定其他微信号");
                 Db::name("user_extract_openid")->insert([
                     'uid' => $uid,
                     'openid' => $unionId,