Fix: Chat Assistant page goes blank #4566 (#4727)

### What problem does this PR solve?

Fix: Chat Assistant page goes blank #4566

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

web/src/pages/chat/markdown-content/index.tsx

   }, [content, loading, t]);
 
   useEffect(() => {
-    setDocumentIds(reference?.doc_aggs?.map((x) => x.doc_id) ?? []);
+    const docAggs = reference?.doc_aggs;
+    setDocumentIds(Array.isArray(docAggs) ? docAggs.map((x) => x.doc_id) : []);
   }, [reference, setDocumentIds]);
 
   const handleDocumentButtonClick = useCallback(