[ML] Anomaly Explorer: Prevent crash on anomaly table filter (elastic#213075)

Fix for: elastic#212569
From what I found, the issue was with the `useUrlStateService` after
changes introduced in elastic#203224,
which made the service more generic.

When filtering causes the `explorer` to remount the `AnomaliesTable`,
pagination state updates are triggered before the effect that sets
`setCallback.current` executes.

Initializing the ref with `setState` ensures its availability from the
first render.


https://github.com/user-attachments/assets/d1aa8409-56e5-4632-a5f2-82350b877db6

Author: rbrtj

x-pack/platform/packages/private/ml/url_state/src/url_state.tsx

@@ -291,7 +291,7 @@ export const useUrlStateService = <K extends Accessor, T>(
     ? state?.[optionsRef.current.pageKey]
     : state;
 
-  const setCallback = useRef<typeof setState>();
+  const setCallback = useRef<typeof setState>(setState);
 
   useEffect(() => {
     setCallback.current = setState;