[BUGFIX] Fix undefined array key warning in DataHandler

Not all tables have tstamp defined in their ctrl section.

Resolves: #97588
Releases: main, 11.5
Change-Id: Ibddaab2e313bc2511b1f9aa903ed312d3cf7f9bd
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74556


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>