[BUGFIX] Fix undefined key warning in ElementInformationController

Since the element information window can also be opened from
an IRRE within a Flexform element, the table name might be
empty and a fallback has to be added when accessing TCA.

Resolves: #96649
Releases: main, 11.5
Change-Id: I5d98e838290ff21b46c764a687703f010f1a50aa
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73176


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