ظهور خطأ عند إستعمال Pusher مع Laravel 8

أستعمل Pusher مع laravel الإصدار 8. عند بث event أتلقى هذا الخطأ. أستطيع أن أرى أن الحدث تم إطلاقه في pusher degub console . أنا لا أفهم سبب هذا الخطأ.

{message: "Undefined property: stdClass::$channels", exception: "ErrorException",…}
exception: "ErrorException"
file: "C:\xampp\htdocs\realtimechat\vendor\pusher\pusher-php-server\src\Pusher.php"
line: 538
message: "Undefined property: stdClass::$channels"
trace: [{file: "C:\xampp\htdocs\realtimechat\vendor\pusher\pusher-php-server\src\Pusher.php", line: 538,…},…]

و هذا الكود الخاص بي:

<?php 
public function sendMessage(Request $request)
{
  event(new MessageEvent('this is my first event'));
}

وهذا صنف ال event:

<?php

namespace App\Events;

use Illuminate\Broadcasting\Channel;
use Illuminate\Broadcasting\InteractsWithSockets;
use Illuminate\Broadcasting\PresenceChannel;
use Illuminate\Broadcasting\PrivateChannel;
use Illuminate\Contracts\Broadcasting\ShouldBroadcast;
use Illuminate\Foundation\Events\Dispatchable;
use Illuminate\Queue\SerializesModels;

class MessageEvent implements ShouldBroadcast
{
  use Dispatchable, InteractsWithSockets, SerializesModels;

  public $message;

  /**
     * Create a new event instance.
     *
     * @return void
     */
  public function __construct($message)
  {
    $this->message = $message;
  }

  /**
     * Get the channels the event should broadcast on.
     *
     * @return \Illuminate\Broadcasting\Channel|array
     */
  public function broadcastOn()
  {
    return new Channel('channel-name');
  }

  public function broadcastAs()
  {
    return 'userChatChannel';
  }

}