title: Symfony 2.1 app.session.flashbag.get('something') returns empty value
body: <p>I have a trouble with using <code>app.session.flashbag.get('notice')</code>. </p>
  
  <p>In the controller I make</p>
  
  <pre><code>public function updateAction(Request $request, $id)
  {
      $em = $this-&gt;getDoctrine()-&gt;getManager();
  
      $entity = $em-&gt;getRepository('SomeBundle:SomeEntity')-&gt;find($id);
  
      $editForm = $this-&gt;createForm(new SomeEntityType(), $entity);
      $editForm-&gt;bind($request);
  
      if ($editForm-&gt;isValid()) {
          $em-&gt;persist($entity);
          $em-&gt;flush();
  
          $flash = $this-&gt;get('translator')-&gt;trans('Some Entity was successfully updated');
          $this-&gt;get('session')-&gt;getFlashBag()-&gt;add('notice', $flash);
  
          return $this-&gt;redirect($this-&gt;generateUrl('some_entity_edit', array('id' =&gt; $id)));
  
      }
  </code></pre>
  
  <p>In editAction I'm getting information from the session:</p>
  
  <pre><code>public function editAction($id)
  {
      $em = $this-&gt;getDoctrine()-&gt;getManager();
  
      $flashes = $this-&gt;get('session')-&gt;getFlashBag()-&gt;get('notice', array());
  
      //...
      //...
  
      return array(
          'entity'      =&gt; $entity,
          'edit_form'   =&gt; $editForm-&gt;createView(),
          'flashes' =&gt; $flashes
      );
  }
  </code></pre>
  
  <p>And  i'm trying in the TWIG get information from the session :</p>
  
  <pre><code>TWIG: {% for flashMessage in app.session.flashbag.get('notice') %}{{ flashMessage }}{% endfor %}
  
  PHP: {% for flashMessage2 in flashes %}{{ flashMessage2 }}{% endfor %}
  </code></pre>
  
  <p>The app.session.flashbag.get('notice') is empty, the flashes has a value.</p>
  
  <p>Do you have any ideas, why I can't get data from the app.session.flashbag.get('notice')?</p>