title: symfony 4 - InvalidArgumentException: The current node list is empty
body: <p>Hi I'm trying to add symfony unit test for a form. This is my code...</p>
  
  <pre><code>$crawler = $this-&gt;client-&gt;request('GET', '/admin/user/new');
  
          $form = $crawler-&gt;selectButton('Save')-&gt;form(array(
              'user[displayName]' =&gt; 'user',
              'user[username]' =&gt; 'user@yahoo.com',
              'user[password]' =&gt; 'user123',
              'user[phoneNumber]' =&gt; '1234789',
              'user[roles]' =&gt; 'ROLE_USER',
          ));
          $crawler = $this-&gt;client-&gt;submit($form);
  
          $crawler = $this-&gt;client-&gt;followRedirect();
  
          $this-&gt;assertGreaterThan(
                  0, $crawler-&gt;filter('html:contains("Le tue modifiche sono state salvate!")')-&gt;count()
          );
  </code></pre>
  
  <p>But I only ends up with this error,</p>
  
  <blockquote>
    <p>InvalidArgumentException: The current node list is empty.</p>
  </blockquote>
  
  <p>It works when <strong>I try with language English</strong> but only fail when I change my default language to Italian in my app.</p>