[BUGFIX] Suggest wizard in FlexForms for new records

Within new records the suggest wizard doesn't work in FlexForm fields.
Due to unexpected incoming data the field configuration can't be fetched.
This patch ensures sanitized data before fetching FlexForms field
configuration.

Resolves: #73864
Releases: master, 7.6
Change-Id: I7e9a72c2aa6d1efed943845aa2198ce153b75fb8
Reviewed-on: https://review.typo3.org/47223


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>