add proptypes

src/components/views/messages/EditHistoryMessage.js

@@ -41,6 +41,8 @@ export default class EditHistoryMessage extends React.PureComponent {
     static propTypes = {
         // the message event being edited
         mxEvent: PropTypes.instanceOf(MatrixEvent).isRequired,
+        previousEdit: PropTypes.instanceOf(MatrixEvent).isRequired,
+        isBaseEvent: PropTypes.bool,
     };
 
     constructor(props) {