improve graphql error handling

web/src/app/arrangementer/page.tsx

@@ -18,19 +18,35 @@ export async function generateMetadata(
   parent: ResolvingMetadata
 ): Promise<Metadata | null> {
   const { data, error } = await getClient().query(eventIndexMetadataQuery, {});
-  const index = (data?.index ?? []) as EventIndexFragment;
 
-  if (!index) {
+  if (error) {
+    throw new Error(error.message);
+  }
+  if (!data?.index) {
     return null;
   }
 
+  const index = data.index as EventIndexFragment;
   const metadata = await getSeoMetadata(index, parent);
   return metadata;
 }
 
 export default async function Page() {
   const { data, error } = await getClient().query(eventsOverviewQuery, {});
-  const index = (data?.index ?? []) as EventIndexFragment;
+  if (error) {
+    throw new Error(error.message);
+  }
+  if (
+    !data?.index ||
+    !data?.events?.futureEvents ||
+    !data?.eventCategories ||
+    !data?.eventOrganizers ||
+    !data?.venues
+  ) {
+    throw new Error("Failed to render /arrangementer");
+  }
+
+  const index = data?.index as EventIndexFragment;
   const events = (data?.events?.futureEvents ?? []) as EventFragment[];
   const eventCategories = (data?.eventCategories ?? []) as EventCategory[];
   const eventOrganizers = (data?.eventOrganizers ?? []) as EventOrganizer[];