message: Fix checks to show prompt to start new chats
  We compared the length of the list rooms but not historical or favourite.
  Caught by new version of typescript when I tried to upgrade.
diff: @@ -547,7 +547,7 @@ export default class RoomList extends React.PureComponent<IProps, IState> {
  const unfilteredHistorical = unfilteredLists[DefaultTagID.Archived] || [];
  const unfilteredFavourite = unfilteredLists[DefaultTagID.Favourite] || [];
  // show a prompt to join/create rooms if the user is in 0 rooms and no historical
  - if (unfilteredRooms.length < 1 && unfilteredHistorical < 1 && unfilteredFavourite < 1) {
  + if (unfilteredRooms.length < 1 && unfilteredHistorical.length < 1 && unfilteredFavourite.length < 1) {
  explorePrompt = <div className="mx_RoomList_explorePrompt">
  <div>{ _t("Use the + to make a new room or explore existing ones below") }</div>
  <AccessibleButton
  