Fix Jitsi widgets causing localized tile crashes

Seems to be that as part of the layout work the timing sequence for when `.getRoom().widgets` will work changed. We can get around this with `initIfNeeded` which will no-op in the worst case.

This also includes a copy change to make ended conferences stop lying about where to find the widget. This is work towards https://github.com/vector-im/element-web/issues/15739

src/stores/WidgetStore.ts

@@ -154,7 +154,8 @@ export default class WidgetStore extends AsyncStoreWithClient<IState> {
         this.emit(UPDATE_EVENT, roomId);
     };
 
-    public getRoom = (roomId: string) => {
+    public getRoom = (roomId: string, initIfNeeded = false) => {
+        if (initIfNeeded) this.initRoom(roomId); // internally handles "if needed"
         return this.roomMap.get(roomId);
     };