[BUGFIX] Prevent undefined array key in DataHandler

Resolves: #96069
Releases: master, 11.5
Change-Id: I2d883ebb7682ac7f402cdcb91b015ca74bdb72b4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72283


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>