[BUGFIX] Do not render empty `eval` and `is_in` instructions

This commit checks whether `eval` and `is_in` are not empty before they
are used as "input params" for the JavaScript part of the FormEngine.

Also, a plausibility check is added to ensure `eval=is_in` and a
non-falsy `is_in` configuration are given.

Resolves: #103184
Releases: main, 12.4
Change-Id: I23da4483f1b35b0720ce59d07847fe01ead9a461
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83085


Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Markus Klein <markus.klein@typo3.org>