“未定义的属性：Illuminate \ Auth \ Events \ Authenticated :: $ guard”

Question

我正在构建laravel（v5.5）MultiAuth应用程序。每当用户/管理员登录/注销时，这段来自Adldap \ Laravel \ Listeners \ BindsLdapUserModel的代码都将引发ErrorException“未定义的属性：Illuminate \ Auth \ Events \ Authenticated :: $ guard”

 public function handle($event)
{
    // Before we bind the users LDAP model, we will verify they are using the Adldap
    // authentication provider, the required trait, the users LDAP property has
    // not already been set, and we have located an LDAP user to bind.

    if (
        $this->isUsingAdldapProvider($event->guard)
        && $this->canBind($event->user)
        && $user = Resolver::byModel($event->user)
    ) {
        $event->user->setLdapUser($user);
    }
}