[BUGFIX] BooleanValidator skips Validation with missing compare param

If no 'is' parameter is given, BooleanValidator skips testing and
returns TRUE. So all properties of type boolean not explicit assigned
to validation pass the test without limitation.

Fixes: #46031
Releases: 6.1
Change-Id: Ib484e35fbb90e3bb878ef5114cf65c05975d0d6e
Reviewed-on: https://review.typo3.org/18705
Reviewed-by: Jost Baron
Tested-by: Jost Baron
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring