我得到以下错误当我尝试登录，我找不到问题在哪里.我使用lumen 9与php 8.1.

<!-- Lcobucci\JWT\Token\Builder::relatedTo(): Argument #1 ($subject) must be of type string, null given, called in /home/ss20nt22/public_html/wms/vendor/php-open-source-saver/jwt-auth/src/Providers/JWT/Lcobucci.php on line 212 (500 Internal Server Error) -->

以下是我的函数：

public function login(Request $request)
    {
        
        $this->validate($request, [
            'nume' => 'required|string',
            'password' => 'required|string',
        ]);
        $credentials = $request->only(['nume', 'password']);
        if (!$token = Auth::attempt($credentials)) {
            // Login has failed
            return response()->json(['message' => 'Unauthorized'], 401);
        }
        return $this->respondWithToken($token);
    }