控制器不存在:app\index\admin\Plugin

        try {            $instance = Loader::controller(                $controller,                $config['url_controller_layer'],                $config['controller_suffix'],                $config['empty_controller']            );        } catch (ClassNotFoundException $e) {            throw new HttpException(404, 'controller not exists:' . $e->getClass());        }        // 获取当前操作名        $action = $actionName . $config['action_suffix'];        $vars = [];        if (is_callable([$instance, $action])) {            // 执行操作方法            $call = [$instance, $action];