title: Symfony passes bad default value to parameter
body: <p>Symfony passes empty value (<code>""</code>) to first parameter.</p>
  
  <p>The controller definition:</p>
  
  <pre><code>/**
  * @Route("/{mediaGenreP}/{mediaLanguageP}/{pageMedia}", name="index", requirements={"mediaGenreP": "\d*", "mediaLanguageP": "\d*"})
  */
  public function indexAction($mediaGenreP = null, $mediaLanguageP = null, $pageMedia = 0);
  </code></pre>
  
  <p>or </p>
  
  <pre><code>/**
  * @Route("/{mediaGenreP}/{mediaLanguageP}/{pageMedia}", name="index", requirements={"mediaGenreP": "\d*", "mediaLanguageP": "\d*"})
  */
  public function indexAction($mediaGenreP = 0, $mediaLanguageP = null, $pageMedia = 0);
  </code></pre>
  
  <p>When I access <code>/</code> or <code>//1</code>, Symfony passes <code>""</code> as the value to <code>mediaGenreP</code>. It was supposed to be <code>0</code> because the default int value is <code>0</code>.</p>