message: require a series on a bar chart in the UI
diff: * under the License.
  */
  import { t } from '@superset-ui/translation';
  +import { nonEmpty } from '../validators';
  export default {
  controlPanelSections: [
  @@ -55,6 +56,7 @@ export default {
  controlOverrides: {
  groupby: {
  label: t('Series'),
  + validators: [nonEmpty],
  },
  columns: {
  label: t('Breakdowns'),
  