[BUGFIX] Fix warning on array key "1"

Patch fixes warning on PHP 8.1 in AbstractItemProvider

Resolves: #98151
Releases: main, 11.5
Change-Id: Ic74ec7771be077aa5e6a84e8db3310fc895dcc02
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75476


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Torben Hansen <derhansen@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>