question: void zApplyAllowEmptyDates ( ) { if ( ! hasParent ( ) ) { return ; } LocalDate selectedDate = zGetParentSelectedDate ( ) ; if ( ( ! allowEmptyDates ) && ( selectedDate == null ) ) { LocalDate today = LocalDate . now ( ) ; if ( InternalUtilities . isDateVetoed ( vetoPolicy , today ) ) { throw new RuntimeException ( "Exception in DatePickerSettings.zApplyAllowEmptyDates(), " + "Could not initialize a null date to today, because today is vetoed by " + "the veto policy. To prevent this exception, always call " + "setAllowEmptyDates() -before- setting a veto policy." ) ; } zSetParentSelectedDate ( today ) ; } }
target:  zApplyAllowEmptyDates, This applies the named setting to the parent component. Implementation Notes: This cannot throw an exception while the parent DatePicker or parent CalendarPanel is being constructed, because a veto policy cannot be set until after the parent component is constructed.