title: Symfony Type error: Too few arguments to function FormRenderer::renderBlock()
body: <p>I got a Form that must to handle the helpdesk requests in Symfony 3.3, i will render this using twig.</p>
  
  <p><strong>Controller</strong></p>
  
  <pre><code>/**
   * @Route("/helpdesk/apri_ticket", name="helpdesk_apri")
   */
  public function helpdeskNewAction(Request $request) {
  
      $entity = new HelpDesk();
  
      $form = $this-&gt;createFormBuilder($entity)
          -&gt;add('title',TextType::class,array(
              'label' =&gt; 'Titolo',
              'attr' =&gt; array('class' =&gt; 'form-control')
          ))
          -&gt;add('type',ChoiceType::class, array(
              'choices' =&gt; array(
                  'Scegli...' =&gt; '0',
                  'Assistenza' =&gt; '1',
                  'Problema' =&gt; '2',
                  'Errore' =&gt; '3'
              )
          ))
          -&gt;add('message', TextType::class, array(
              'label' =&gt; 'Messaggio',
              'attr' =&gt; array('class' =&gt; 'form-control')
          ))
          -&gt;add('submit',SubmitType::class, array(
              'label' =&gt; 'Apri Ticket',
              'attr' =&gt; array('class' =&gt; 'btn-success')
          ))
          -&gt;getForm();
  
      $form-&gt;handleRequest($request);
  
      if($form-&gt;isSubmitted() &amp;&amp; $form-&gt;isValid()) {
          print 'ok';
      }
  
      return $this-&gt;render('help/help.create.html.twig', array(
          'form' =&gt; $form-&gt;createView())
      );
  }
  </code></pre>
  
  <p>Here is the easy twig template:</p>
  
  <pre><code>{{ form_start(form) }}
      {{ form_widget(form.title) }}
      {{ form_widget(form.type) }}
      {{ form_widget(form.message) }}
  {{ form_end() }}
  </code></pre>
  
  <p>Here is the Error:</p>
  
  <pre><code>Type error: Too few arguments to function Symfony\Component\Form\FormRenderer::renderBlock(), 0 passed in /vendor/twig/twig/lib/Twig/Environment.php(462) : eval()'d code on line 83 and at least 2 expected
  </code></pre>
  
  <p>What's wrong with this? FormRenderer::renderBlock ask for at least 2 arguments, FormView and BlockName and optional an array containing variables. This is the first time I got this error and I don't know what is this BlockName.</p>