Fixed #11675 ValueToDuplicatesTransformer accept "0" value

Fixed wrong return null syntax

Added transformation to null on empty arrays

Removed useless statement in condition and switched to yoda condition
Merge branch '2.3' into 2.4

* 2.3:
  [DependencyInjection] fix @return anno created by PhpDumper
  Fixed the phpdoc of the VoterInterface
  [DoctrineBridge] Fix empty parameter logging in the dbal logger
  Fixed #11675 ValueToDuplicatesTransformer accept "0" value
  check for the correct field type
  fix handling of nullable XML attributes
  [DomCrawler] fix the axes handling in a bc way

Conflicts:
	src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php