[BUGFIX] Skip empty static routes

Due to incomplete editing in the site module or wrong yaml configuration
it is possible that an empty static route is defined which will break
the complete frontend.

Skip empty routes as those don't make any sense.

Resolves: #87500
Releases: master, 9.5
Change-Id: I9f5737bf077fd3b2f0c38522ee3ae641c7e5cd21
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63610


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: Susanne Moog <look@susi.dev>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Susanne Moog <look@susi.dev>