[BUGFIX] Avoid building SQL deleteClause expression if unused

This patch avoids building an instance of ConnectionPool,
getting a QueryBuilder and building an expression unless
that expression is needed by the function.

Also switches a condition with else clause to an early
return guard clause (cosmetic only).

Change-Id: I804b3ff9e624aa4b8b9c760d2a5e858039b6f9b9
Resolves: #78806
Releases: master
Reviewed-on: https://review.typo3.org/50784


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Stephan Großberndt <stephan@grossberndt.de>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>