Fix room list not being cleared (#32436)

* Fix room list not being cleared

RoomListV3 was lacking an onNotReady which meant that the room list
would sometimes not be cleared between logins.

* Fix return type

Co-authored-by: Florian Duros <florianduros@element.io>

---------

Co-authored-by: Florian Duros <florianduros@element.io>

src/stores/room-list-v3/RoomListStoreV3.ts

@@ -161,6 +161,10 @@ export class RoomListStoreV3Class extends AsyncStoreWithClient<EmptyObject> {
         this.emit(LISTS_UPDATE_EVENT);
     }
 
+    protected async onNotReady(): Promise<void> {
+        this.roomSkipList = undefined;
+    }
+
     protected async onAction(payload: ActionPayload): Promise<void> {
         if (!this.matrixClient || !this.roomSkipList?.initialized) return;