Form validation in Symfony2 wont go away - php

Question

I made this Controller to play around with Symfony 2.3
namespace AskThem\MainBundle\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\Request;
use AskThem\MainBundle\Entity\Task;
class DefaultController extends Controller {
private $context = array();
public function indexAction(Request $request) {
$task = new Task();
$form =
$this->createFormBuilder($task)
->add("task", "text")
->add("dueDate", "date")
->add("save", "submit")
->add("saveAndAdd", "submit")
->getForm();
$form->handleRequest($request);
if ($form->isValid()) {
// ... perform some action, such as saving the task to the database
$nextAction = $form->get('saveAndAdd')->isClicked()
? 'homepage'
: 'task_success';
return $this->redirect($this->generateUrl($nextAction));
}
$this->context["form"] = $form->createView();
return $this->render('AskThemMainBundle:Default:index.html.twig', $this->context);
}
public function successAction(Request $request) {
return new Response("Victory");
}
}
The form was working fine, so then I added a validation-yml file with some NotBlank rules to test if it would work, and indeed it did.
But when I deleted those rules (I even deleted the whole file) the form still kept presenting itself with the required attribute. How do I turn off the validation?