[BUGFIX] Catch exceptions for invalid form configuration files

Resolves: #84859
Releases: master, 8.7
Change-Id: I64b14c87758178f76258bdbf747931b008d9a71c
Reviewed-on: https://review.typo3.org/56797


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>