Fix TimelineReset handling when no room associated (#9553)

Author: Germain

src/indexing/EventIndex.ts

@@ -241,8 +241,8 @@ export default class EventIndex extends EventEmitter {
      * Listens for timeline resets that are caused by a limited timeline to
      * re-add checkpoints for rooms that need to be crawled again.
      */
-    private onTimelineReset = async (room: Room, timelineSet: EventTimelineSet, resetAllTimelines: boolean) => {
-        if (room === null) return;
+    private onTimelineReset = async (room: Room | undefined) => {
+        if (!room) return;
         if (!MatrixClientPeg.get().isRoomEncrypted(room.roomId)) return;
 
         logger.log("EventIndex: Adding a checkpoint because of a limited timeline",