[BUGFIX] Fix notice in GridColumnItem

Fix a notice which happens if the exclude configuration of
the field `hidden` of tt_content is removed.

Resolves: #96873
Releases: main, 11.5
Change-Id: I94a0ff88a936f403dcd8000f691ae5334863d07f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73468


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>