Fix getAlertSummary returning 400 (Bad Request) (#199116)

Fixes #190126
Fixes #184649

## Summary

This PR fixes alert summary API returning 400 when there is no featured
by only sending this request when featureId is available, otherwise
showing a default state as shown below:

#### Alert details page

|With featureId | Without featureId (intermediate state)|
|---|---|

|![image](https://github.com/user-attachments/assets/d4b4be5a-43be-4365-bd28-66c9dd53d979)|![image](https://github.com/user-attachments/assets/be437052-7c94-4d89-9238-b63264a812c8)|

#### Rule details page
|With featureId | Without featureId|
|---|---|

|![image](https://github.com/user-attachments/assets/28ff4ac5-ffc7-4c9e-8087-408f2ccff98e)|![image](https://github.com/user-attachments/assets/b82f530e-a27c-44e5-a241-c179bc8f1f46)|

x-pack/packages/observability/alert_details/src/hooks/use_alerts_history.ts

@@ -55,6 +55,7 @@ export function useAlertsHistory({
   http,
   instanceId,
 }: Props): UseAlertsHistory {
+  const enabled = !!featureIds.length;
   const { isInitialLoading, isLoading, isError, isSuccess, isRefetching, data } = useQuery({
     queryKey: ['useAlertsHistory'],
     queryFn: async ({ signal }) => {
@@ -71,10 +72,11 @@ export function useAlertsHistory({
       });
     },
     refetchOnWindowFocus: false,
+    enabled,
   });
   return {
     data: isInitialLoading ? EMPTY_ALERTS_HISTORY : data ?? EMPTY_ALERTS_HISTORY,
-    isLoading: isInitialLoading || isLoading || isRefetching,
+    isLoading: enabled && (isInitialLoading || isLoading || isRefetching),
     isSuccess,
     isError,
   };

x-pack/plugins/triggers_actions_ui/public/application/hooks/use_load_alert_summary.ts

@@ -102,16 +102,18 @@ async function fetchAlertSummary({
   timeRange: AlertSummaryTimeRange;
   filter?: estypes.QueryDslQueryContainer;
 }): Promise<AlertSummary> {
-  const res = await http.post<AsApiContract<any>>(`${BASE_RAC_ALERTS_API_PATH}/_alert_summary`, {
-    signal,
-    body: JSON.stringify({
-      fixed_interval: fixedInterval,
-      gte: utcFrom,
-      lte: utcTo,
-      featureIds,
-      filter: [filter],
-    }),
-  });
+  const res = featureIds.length
+    ? await http.post<AsApiContract<any>>(`${BASE_RAC_ALERTS_API_PATH}/_alert_summary`, {
+        signal,
+        body: JSON.stringify({
+          fixed_interval: fixedInterval,
+          gte: utcFrom,
+          lte: utcTo,
+          featureIds,
+          filter: [filter],
+        }),
+      })
+    : {};
 
   const activeAlertCount = res?.activeAlertCount ?? 0;
   const activeAlerts = res?.activeAlerts ?? [];