[BUGFIX] Change 3rd argument of calls to callUserFunction()

The third argument of `GeneralUtility::callUserFunction` must be either
an object or null.
Ensure the argument is always null instead of false to avoid
triggering a deprecation log entry.

Resolves: #91184
Releases: master
Change-Id: I5ee0a58d812de737bd631e5c1986895e69c158af
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64415


Tested-by: Josef Glatz <josefglatz@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>