message: [BUG] Fix undefined prop-type
diff: @@ -129,7 +129,7 @@ class Popover extends Component {
  usePortal: PropTypes.bool,
  modifiers: PropTypes.shape(),
  arrowRenderer: PropTypes.func,
  - referenceElement: PropTypes.instanceOf(HTMLElement)
  + referenceElement: PropTypes.element
  };
  static defaultProps = {
  