[TASK] Inform user if TS condition does not make sense

Empty conditions `[]` always evaluate to false. Warn the user
if such a condition is present.

Resolves: #84911
Releases: master, 8.7
Change-Id: I499e64aad30e29fe3698c40fed57e1f1c87ce885
Reviewed-on: https://review.typo3.org/56835


Reviewed-by: Robert Wildling <robertwildling@gmail.com>
Tested-by: Robert Wildling <robertwildling@gmail.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Riny van Tiggelen <info@online-gamer.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>