message: read collapsedRhs from props when mounting main split
diff: @@ -55,7 +55,7 @@ export default class MainSplit extends React.Component {
  }
  componentDidMount() {
  - if (this.props.panel && !this.collapsedRhs) {
  + if (this.props.panel && !this.props.collapsedRhs) {
  this._createResizer();
  }
  }
  