message: Fix MainSplit IProps
diff: @@ -24,7 +24,7 @@ import { Direction } from "re-resizable/lib/resizer";
  interface IProps {
  resizeNotifier: ResizeNotifier;
  collapsedRhs?: boolean;
  - panel: JSX.Element;
  + panel?: JSX.Element;
  }
  @replaceableComponent("structures.MainSplit")
  