[BUGFIX] Avoid fatal error with invalid soft reference parser links

When a link href is empty or invalid, TYPO3 now does not
crash anymore.

Resolves: #100958
Releases: main, 12.4
Change-Id: I768d43b72a3abd55af06cd9750ac8a400bc41d63
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79462


Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Benni Mack <benni@typo3.org>