我正在使用谷歌API，并面临以下错误-
未定义的索引：在574中，在/供应商/谷歌/apiclient/src/client. php中过期。
我不知道这个错误意味着什么，当我检查它被写的文件-

if (!isset($this->token['expires_in'])) {
            // if the token does not have an "expires_in", then it's considered expired
            return true;
        }
        // If the token is set to expire in the next 30 seconds.
        return ($created + ($this->token['expires_in'] - 30)) < time();

您能告诉我这个错误是什么意思，以及我如何解决它吗？
这是我的自定义代码-

if (file_exists($credentialsPath)) {
        $accessToken = json_decode(file_get_contents($credentialsPath), true);
    } else {
        $authUrl = $client->createAuthUrl();
        printf("Open the following link in your browser:\n%s\n", $authUrl);
        print 'Enter verification code: ';
        $authCode = trim(fgets(STDIN));
        $accessToken = $client->fetchAccessTokenWithAuthCode($authCode);
        if (!file_exists(dirname($credentialsPath))) {
            mkdir(dirname($credentialsPath), 0700, true);
        }
        file_put_contents($credentialsPath, json_encode($accessToken));
    }
    $client->setAccessToken($accessToken);
    if ($client->isAccessTokenExpired()) {
        $client->fetchAccessTokenWithRefreshToken($client->getRefreshToken());
        file_put_contents($credentialsPath, json_encode($client->getAccessToken()));
    }