public function getUnthemedIssues($publication)
{
Validation::notEmpty($publication, 'publication');
$issues = array();
$em = $this->getManager();
// we need to find if the theme is used by anyoane.
$q = $em->createQueryBuilder();
$q->select('iss')->from(Issue::NAME, 'iss')->leftJoin('iss.outputSettingsIssues', 'osi')->where('iss.publication = :publication')->andWhere('osi.id IS NULL')->setParameter('publication', $publication);
$issues = $q->getQuery()->getResult();
return $issues;
}