[BUGFIX] Cast indexer config to integers before multiplication

If either the options `minAge` or `maxAge` are an empty string, the
corresponding multiplication will fail and a PHP warning is triggered.

As a quick win, the values are casted to integers.

Resolves: #90087
Releases: master, 9.5, 8.7
Change-Id: Ia6861434231e7e338384c3e919a09466b39d425f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62846


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>