message: add emptyLabel prop to DateTextField
diff: @@ -22,6 +22,7 @@ export default class DateTextField extends PureComponent {
  onChange: PropTypes.func.isRequired,
  onClick: PropTypes.func.isRequired,
  invalidLabel: PropTypes.string,
  + emptyLabel: PropTypes.string,
  labelFunc: PropTypes.func,
  keyboard: PropTypes.bool,
  InputProps: PropTypes.shape(),
  @@ -32,6 +33,7 @@ export default class DateTextField extends PureComponent {
  static defaultProps = {
  disabled: false,
  invalidLabel: 'Unknown',
  + emptyLabel: '',
  value: new Date(),
  labelFunc: undefined,
  format: undefined,
  @@ -47,15 +49,21 @@ export default class DateTextField extends PureComponent {
  value,
  format,
  invalidLabel,
  + emptyLabel,
  labelFunc,
  } = props;
  + const isEmpty = value === null;
  const date = moment(value);
  if (labelFunc) {
  return labelFunc(date, invalidLabel);
  }
  + if (isEmpty) {
  + return emptyLabel;
  + }
  +
  return date.isValid()
  ? date.format(format)
  : invalidLabel;
  @@ -120,6 +128,7 @@ export default class DateTextField extends PureComponent {
  disabled,
  onClick,
  invalidLabel,
  + emptyLabel,
  labelFunc,
  keyboard,
  value,
  