[BUGFIX] Form wizard: Removed call to deprecated method render()

Call of FlashMessage->render() if no reference to record
was replaced with appropriate code.

Resolves: #73546
Releases: master, 7.6
Change-Id: I3fa0285ccd68d7a62d63df60b488bb1fb561a243
Reviewed-on: https://review.typo3.org/46765


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>