1. 修复获取access_token时出现的报错bug

Author: shinn-lancelot

src/MiniProgram.php

@@ -53,7 +53,7 @@ public function getAccessTokenData()
         );
         $url = self::API_HOST . self::ACCESS_TOKEN_PATH . http_build_query($urlParamArr);
         $res = json_decode(Common::httpRequest($url), true);
-        if ($res['errcode']) {
+        if (isset($res['errcode']) && $res['errcode']) {
             return '';
         } else {
             return $res;