[BUGFIX] Prevent undefined array key warnings in PageRepository

Resolves: #96913
Releases: main, 11.5
Change-Id: Idf1b2d34d9c4373f52f5d8cbae84d83d2d5bfbd3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73535


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Bartsch <bo@cedev.de>