fix: Handle empty stack ref in useAssistiveHideSiblings

Fixes a rare issue when the popup model's stack ref is `undefined`. This will mostly happen in `StrictMode`.

modules/react/popup/lib/hooks/useAssistiveHideSiblings.ts

@@ -23,7 +23,7 @@ export const useAssistiveHideSiblings = createElemPropsHook(usePopupModel)(model
     }
 
     const siblings = [
-      ...((model.state.stackRef.current?.parentElement?.children as any) as HTMLElement[]),
+      ...((model.state.stackRef.current?.parentElement?.children || []) as HTMLElement[]),
     ].filter(el => el !== model.state.stackRef.current);
     const prevAriaHidden = siblings.map(el => el.getAttribute('aria-hidden'));
     siblings.forEach(el => {