Skip useOnlineBoard fetch when dateFrom/dateTo are empty

Details page calls useOnlineBoard to populate the sibling mini-list,
passing empty-string params when the URL has no ?request=... context.
The empty params were reaching the backend as dateFrom=&dateTo=, which
returns HTTP 400 and surfaces as an error in the browser console.

Short-circuit the effect so we just emit an empty result when either
range bound is missing — same no-fetch behavior, no console noise.

src/features/online-board/hooks/useOnlineBoard.ts

@@ -43,6 +43,17 @@ export function useOnlineBoard(
   }, []);
 
   useEffect(() => {
+    // Callers pass empty strings when the search context isn't resolved
+    // yet (e.g. details page with no `?request=...`). Skip the fetch
+    // rather than sending `dateFrom=&dateTo=` — the backend rejects that
+    // with HTTP 400 and it shows up as an error in the browser console.
+    if (!params.dateFrom || !params.dateTo) {
+      setFlights([]);
+      setLoading(false);
+      setError(null);
+      return;
+    }
+
     let cancelled = false;
     setLoading(true);
     setError(null);