code: @Override
      public void onValueUnRestricted(final String value) {
          this.restrictedColumns.remove(value);
          
          // Check single column used in data set -> it cannot be unselected.
          if (listEditor.getList().size() == 1) {
              setEditorEnabled(0 ,false, DataSetEditorConstants.INSTANCE.dataSetMustHaveAtLeastOneColumn());
          } else {
              setEditorEnabled(value, true, null);
          }
      }
docs: Set the column that can be removed again from the list, as it's no longer used by the filter.
  @param value The column id.