[BUGFIX] Prevent undefined index warning in ExtensionManagementUtility

Resolves: #95729
Releases: master
Change-Id: I5020a42d156dbd15202228e963fd8853e123b8bf
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72209


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>