symfony 4-InvalidArgumentException:当前节点列表为空

$crawler = $this->client->request('GET', '/admin/user/new');

        $form = $crawler->selectButton('Save')->form(array(
            'user[displayName]' => 'user',
            'user[username]' => 'user@yahoo.com',
            'user[password]' => 'user123',
            'user[phoneNumber]' => '1234789',
            'user[roles]' => 'ROLE_USER',
        ));
        $crawler = $this->client->submit($form);

        $crawler = $this->client->followRedirect();

        $this->assertGreaterThan(
                0, $crawler->filter('html:contains("Le tue modifiche sono state salvate!")')->count()
        );

但我最后只犯了这个错误,

我试着用语言英语