[BUGFIX] Fix invalid array access in ImageManipulation/Ratio

This also allows automated testing with a minimal data.

Resolves: #100430
Related: #100249
Releases: main, 11.5
Change-Id: I2cee7ff96dee58ef76ce8f91161ed21e1a52553a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78438


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>