code: void zApplyAllowEmptyDates() {
          // If we don't have a parent, then there is nothing to do here. (So, we return.)
          if (!hasParent()) {
              return;
          }
          // Find out if we need to initialize a null date.
          LocalDate selectedDate = zGetParentSelectedDate();
          if ((!allowEmptyDates) && (selectedDate == null)) {
              // We need to initialize the current date, so find out if today is vetoed.
              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.");
              }
              // Initialize the current date.
              zSetParentSelectedDate(today);
          }
      }
docs: 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.