[BUGFIX] RadioViewHelper correct property checked mapping

AbstractEntity objects are not correctly mapped as checked.
Previously the checked comparison failed because the value
attribute was converted to the identifier but not the property value.

Change-Id: I2f2500b394522647c4c87ed29b6f5cabbe009a9c
Resolves: #70303
Releases: master
Reviewed-on: https://review.typo3.org/43736


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>