[BUGFIX] Prevent undefined array index in GifBuilder

Unset non matching key arrays and additionally
secure the array access with a corresponding
check.

Resolves: #102241
Releases: main, 12.4
Change-Id: If034faf04f52f6e8882dd0b610fa5dfdf9ec2298
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83570


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