[BUGFIX] Handle missing $_SERVER['PATH_INFO']

Fix PHP8 warning issue if $_SERVER['PATH_INFO'] is not set.

Resolves: #96373
Releases: main, 11.4
Change-Id: I427aee39c6f6389e418f27474c01cbfd973355e1
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72696


Tested-by: Simon Gilli <typo3@gilbertsoft.org>
Tested-by: Johannes Kasberger <johannes.kasberger@reelworx.at>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Helmut Hummel <typo3@helhum.io>
Reviewed-by: Simon Gilli <typo3@gilbertsoft.org>
Reviewed-by: Johannes Kasberger <johannes.kasberger@reelworx.at>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Helmut Hummel <typo3@helhum.io>