Laravel 接入 jwt-auth 时一个疑似插件问题的报错？

在用laravel-v5.6.28接入插件"tymon/jwt-auth":1.0.0-rc.2时
按照常规步骤接入，一切OK，最后通过Post慢进行接口测试时报错
我故意没有在Authorization里面选择Type。原本应该使用Bearer Token验证，这里我留空了。
报错内容：
Argument 1 passed to Symfony\Component\HttpKernel\Exception\UnauthorizedHttpException::__construct() must be of the type string, null given, called in /......./vendor/dingo/api/src/Auth/Auth.php on line 113

查看这行代码

protected function throwUnauthorizedException(array $exceptionStack)
{
    $exception = array_shift($exceptionStack);

    if ($exception === null) {
        $exception = new UnauthorizedHttpException(null, 'Failed to authenticate because of bad credentials or an invalid authorization header.');
    }

    throw $exception;
}

不怎么会用markdown将就看下吧】
$exception = new UnauthorizedHttpException(null, 'Failed to authenticate because of bad credentials or an invalid authorization header.');
是报错的行数，正常来讲这里应该抛出一个401的异常，并附带message“Failed to authenticate because of bad credentials or an invalid authorization header.”才对，但是却抛出了一个500的异常，Argument 1 passed to UnauthorizedHttpException::__construct() must be of the type string, null given.

通过UnauthorizedHttpException这个类可以看到，

 namespace Symfony\Component\HttpKernel\Exception;

 class UnauthorizedHttpException extends HttpException
 {

        public function __construct(string $challenge, string $message = null, \Exception $previous = null, ?int $code = 0, array $headers = array())
         {
               $headers['WWW-Authenticate'] = $challenge;

               parent::__construct(401, $message, $previous, $headers, $code);
            }
 }

____ construct 方法的第一个参数规定为string格式，但Auth.php传的时候是null，这里应该是框架和插件冲突了吧？还是其他什么问题？

有大佬能帮我解答一下嘛？