[BUGFIX] Fix early return in addUnionStatement method

Set $propertyPath, $tableName and $className to avoid
unnecessary joins and wrong repository results.

This is a regression fix after the Doctrine migration.

Resolves: #79286
Related: #77379
Releases: master
Change-Id: I64489b46b9ca751535b64482f54ceb7b2da05003
Reviewed-on: https://review.typo3.org/51290


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>