array_key_exists() expects parameter 2 to be array, null given

[Abonive]

I have implemented everything like in the guide.

But when I try to request token I get this error
array_key_exists() expects parameter 2 to be array, null given

and it refers to this section

        $body = (parent::issueToken($request));
        $token = json_decode($body, true);
 
        if (array_key_exists('error', $token)) {
            return response()->json([
                'error' => $token['error'],
                'status_code' => 401
            ], 401);
        }

in the issueToken method

[jsdecena]

Can you try

        if (isset(token['error']) && array_key_exists('error', $token)) {
            return response()->json([
                'error' => $token['error'],
                'status_code' => 401
            ], 401);
        }