isset中的偏移类型无效，或在laravel文件auth manager.php中为空

Question

受保护的函数resolve（$ name）     {         $ config = $ this-> getConfig（$ name）;

    if (is_null($config)) {
        throw new InvalidArgumentException("Auth guard [{$name}] is not defined.");
    }

    if (isset($this->customCreators[$config['driver']])) {
        return $this->callCustomCreator($name, $config);
    }

    $driverMethod = 'create'.ucfirst($config['driver']).'Driver';

    if (method_exists($this, $driverMethod)) {
        return $this->{$driverMethod}($name, $config);
    }

    throw new InvalidArgumentException("Auth driver [{$config['driver']}] for guard [{$name}] is not defined.");
}