[BUGFIX] Do not use rowCount() in linkvalidator report

As `rowCount()` is not supported across all DBMS (e.g. sqlite).

The logic is kept, but instead of relying on row count, the list of
items is built first, and checked afterwards.

Resolves: #90231
Releases: master
Change-Id: Iad0dc46c507d300708c9bc9d53aad6d6840a3446
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63061


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Sybille Peters <sypets@gmx.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Sybille Peters <sypets@gmx.de>
Reviewed-by: Benni Mack <benni@typo3.org>