[TASK] Avoid pointless finisher override checkbox

The form plugin now only renders the checkbox for overriding
the finishers if finishers are available at all. Also finishers
without options are ignored.

Resolves: #84774
Releases: master
Change-Id: I1165d054340457fdd219024f28b877a21458b603
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60570


Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Dominik Merkel <merkel.dominik@googlemail.com>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Dominik Merkel <merkel.dominik@googlemail.com>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>