[BUGFIX] Prevent rendering FlexForm diff of deleted records in history

When the record does not exist anymore, then the FlexForm definition
might also not exist anymore (imagine a removed plugin) and it results
in an Exception.

Resolves: #102656
Releases: main, 12.4
Change-Id: I3eac287a50366ae8ca66416080738634eb65ae97
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84643


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>