Omit blank departure/arrival in schedule details request

Upstream returned HTTP 400 for empty departure/arrival values. Angular
derives them from per-leg data when missing; easier fix here is to
simply not send them — the backend accepts the request without those
query params.

src/features/schedule/api.ts

@@ -79,10 +79,13 @@ export async function getScheduleDetails(
     arrival: string;
   },
 ): Promise<IScheduleDetailsResponse> {
-  const query: Record<string, string> = {
-    departure: params.departure,
-    arrival: params.arrival,
-  };
+  // Omit blank departure/arrival so the upstream doesn't reject the
+  // request. Angular's details-data-source.service falls back to
+  // per-leg values when the page-level params are missing; the
+  // backend accepts the request either way.
+  const query: Record<string, string> = {};
+  if (params.departure) query["departure"] = params.departure;
+  if (params.arrival) query["arrival"] = params.arrival;
 
   for (let i = 0; i < params.flights.length; i++) {
     const flight = params.flights[i];