[APM] Fix service maps not loading when there are no APM ML jobs (#69240

)

* Closes #69238 by handling 404 thrown error from the query for APM ML jobs.

* Improved coded readability

* moved anomaly job fetch to new function getApmAnomalyDetectionJobs for
improved readability and only handle a 404 status code response else throw

x-pack/plugins/apm/server/lib/service_map/get_service_anomalies.ts

@@ -8,12 +8,33 @@ import { leftJoin } from '../../../common/utils/left_join';
 import { Job as AnomalyDetectionJob } from '../../../../ml/server';
 import { PromiseReturnType } from '../../../typings/common';
 import { IEnvOptions } from './get_service_map';
+import { Setup } from '../helpers/setup_request';
 import {
   APM_ML_JOB_GROUP_NAME,
   encodeForMlApi,
 } from '../../../common/ml_job_constants';
 
+async function getApmAnomalyDetectionJobs(
+  setup: Setup
+): Promise<AnomalyDetectionJob[]> {
+  const { ml } = setup;
+
+  if (!ml) {
+    return [];
+  }
+  try {
+    const { jobs } = await ml.anomalyDetectors.jobs(APM_ML_JOB_GROUP_NAME);
+    return jobs;
+  } catch (error) {
+    if (error.statusCode === 404) {
+      return [];
+    }
+    throw error;
+  }
+}
+
 type ApmMlJobCategory = NonNullable<ReturnType<typeof getApmMlJobCategory>>;
+
 export const getApmMlJobCategory = (
   mlJob: AnomalyDetectionJob,
   serviceNames: string[]
@@ -62,7 +83,10 @@ export async function getServiceAnomalies(
     return [];
   }
 
-  const { jobs: apmMlJobs } = await ml.anomalyDetectors.jobs('apm');
+  const apmMlJobs = await getApmAnomalyDetectionJobs(options.setup);
+  if (apmMlJobs.length === 0) {
+    return [];
+  }
   const apmMlJobCategories = apmMlJobs
     .map((job) => getApmMlJobCategory(job, serviceNames))
     .filter(