[BUGFIX] Respect nullable date time fields

Nullable time fields with value null (not set) are reset to 0 on update.
This changes the value from not set to midnight.

It is not so problematic for date fields as there reset value,
for the time being, is null also. But this behavior is wrong anyway.

Resolves: #99847
Releases: main, 12.4, 11.5
Change-Id: I080b6bb1ad00a025967d9626632ff71b8fb2193a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79748


Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>