message: Monitoring: Remove unused error handling
  The call to `${alertManagerBaseURL}/api/v1/alerts` is no longer being
  made.
diff: @@ -917,9 +917,7 @@ export class MonitoringUI extends React.Component<null, null> {
  const {alertManagerBaseURL} = (window as any).SERVER_FLAGS;
  if (!alertManagerBaseURL) {
  - const e = new Error('alertManagerBaseURL not set');
  - store.dispatch(UIActions.monitoringErrored('alerts', e));
  - store.dispatch(UIActions.monitoringErrored('silences', e));
  + store.dispatch(UIActions.monitoringErrored('silences', new Error('alertManagerBaseURL not set')));
  return;
  }
  