[BUGFIX] Fix broken back button in EXT:form

This patch fix a regression, introduced with #82668

Resolves: #83057
Related: #82668
Releases: master, 8.7
Change-Id: I421be116be6696c52733a77a94a61f81c84864f4
Reviewed-on: https://review.typo3.org/54716


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Felix Nagel <info@felixnagel.com>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>