Merge pull request #218 from sunnyalways/master

处理return_url为空签名失败的情况

src/Gateways/Alipay/AliBaseObject.php

@@ -231,6 +231,7 @@ private function getBaseData(string $method, array $bizContent)
             // 'app_auth_token' => '', // 暂时不用
             'biz_content' => json_encode($bizContent, JSON_UNESCAPED_UNICODE),
         ];
+        $requestData = ArrayUtil::paraFilter($requestData);
         return ArrayUtil::arraySort($requestData);
     }