message: don't open right panel when switching room again
  a view_right_panel_phase is dispatched by RoomHeaderButtons
  on view_room, which was triggering this to show the panel again.
  Check the fromHeader flag just like when hiding the panel so
  only room header buttons can hide or show the right panel
diff: @@ -59,7 +59,7 @@ export default class HeaderButtons extends React.Component {
  phase: null,
  });
  } else {
  - if (this.props.collapsedRhs) {
  + if (this.props.collapsedRhs && payload.fromHeader) {
  dis.dispatch({
  action: 'show_right_panel',
  });
  