add NotifPanel dot back. (#9242)

partially fixes https://github.com/vector-im/element-web/issues/17641
provides a dot, but not a badge. fixes chronic bug 87.

src/components/views/right_panel/HeaderButtons.tsx

@@ -35,6 +35,7 @@ interface IState {
     headerKind: HeaderKind;
     phase: RightPanelPhases;
     threadNotificationColor: NotificationColor;
+    globalNotificationColor: NotificationColor;
 }
 
 interface IProps {}
@@ -51,6 +52,7 @@ export default abstract class HeaderButtons<P = {}> extends React.Component<IPro
             headerKind: kind,
             phase: rps.currentCard.phase,
             threadNotificationColor: NotificationColor.None,
+            globalNotificationColor: NotificationColor.None,
         };
     }