Doctrine: get single row or null

$query->getOneOrNullResult();

• no result: return null
• more than one result: throw an NonUniqueResultException exception

http://doctrine-orm.readthedocs.org/en/latest/reference/dql-doctrine-query-language.html#query-result-formats

https://github.com/doctrine/doctrine2/blob/master/lib/Doctrine/ORM/AbstractQuery.php#L763