[BUGFIX] Catch invalid Enum value

To avoid breaking the backend, any exception of the JsConfirmation
must be caught and the default value must be returned.

Resolves: #76719
Releases: master, 7.6
Change-Id: Idfea9ec8aa269ac807bf6936263da9803ea39bf8
Reviewed-on: https://review.typo3.org/49695


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Sascha Egerer <sascha@sascha-egerer.de>
Tested-by: Sascha Egerer <sascha@sascha-egerer.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>