[BUGFIX] Fix undefined key warning in indexed_search

Resolves: #99270
Related: #99572
Releases: main, 11.5
Change-Id: I0b3aed81b7ee5d8449c1db962b423fc4fb542287
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77575


Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>