Maybe a bug in EntityRepository?

UserRepository.php

<?php

namespace Vita\UserBundle\Entity;

use Symfony\Component\Security\Core\User\UserProviderInterface;
use Symfony\Component\Security\Core\User\UserInterface;
use Symfony\Component\Security\Core\Exception\UsernameNotFoundException;
use Symfony\Component\Security\Core\Exception\UnsupportedUserException;
use Doctrine\ORM\EntityRepository;
use Doctrine\ORM\NoResultException;
use Vita\UserBundle\Entity\User;

/**
 * Vita\UserBundle\Entity\UserProvider
 */
class UserRepository extends EntityRepository implements UserProviderInterface {

	public function loadUserByUsername($username) {

		/*
		 * The QueryBuilder from EntityRepository does not work properly. The email field throws an error "not defined".
		 * But in the Model it still defined. Without the email in the Query the authentication still fails.
		 */
		
		/*$query = $this->createQueryBuilder('u')
			->where('u.username = :username OR u.email = :email')
			->setParameter('username', $username)
			->setParameter('email', $username)
			->getQuery();*/

		$query = $this->getEntityManager()->getRepository('VitaUserBundle:User')->createQueryBuilder('u')
			->where('u.username = :username OR u.email = :email')
			->setParameter('username', $username)
			->setParameter('email', $username)
			->getQuery();

		try {
			$user = $query->getSingleResult();
		} catch (NoResultException $e) {
			throw new UsernameNotFoundException(sprintf('Unable to find an active admin VitaUserBundle:User object identified by "%s".', $username), null, 0, $e);
		}

		return $user;
	}

	public function refreshUser(UserInterface $user) {

		$class = get_class($user);

		if (!$this->supportsClass($class)) {
			throw new UnsupportedUserException(sprintf('Instances of "%s" are not supported.', $class));
		}

		return $this->loadUserByUsername($user->getUsername());
	}

	public function supportsClass($class) {
		return $this->getEntityName() === $class || is_subclass_of($class, $this->getEntityName());
	}


}