[FOLLOWUP][BUGFIX] Prevent validation from altering the field value

This follow up ensures the initialization of the value.

Resolves: #76124
Releases: master
Change-Id: Ie9981971e97d740df1df8545eb2bbd2dae0b465e
Reviewed-on: https://review.typo3.org/48084


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Tomita Militaru <militarutomita@gmail.com>
Reviewed-by: Nikola Stojiljković <nikola.stojiljkovic@essentialdots.com>
Tested-by: Nikola Stojiljković <nikola.stojiljkovic@essentialdots.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>