[BUGFIX] Fix another PHP 8 warning in DataHandler

Resolves: #102134
Releases: main, 12.4, 11.5
Change-Id: I3aaf6f2c8161579394a0dbe1c9f470edeb0a8bca
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81398


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>