message: make resizeNotifier optional in MainSplit for GroupView
diff: @@ -27,8 +27,10 @@ export default class MainSplit extends React.Component {
  _onResized(size) {
  window.localStorage.setItem("mx_rhs_size", size);
  + if (this.props.resizeNotifier) {
  this.props.resizeNotifier.notifyRightHandleResized();
  }
  + }
  _createResizer() {
  const classNames = {
  