set blank response when indexNotFound exception (opensearch-project#1125

) (opensearch-project#1126)

(cherry picked from commit 65c1519)

Signed-off-by: Riya Saxena <[email protected]>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

src/main/java/org/opensearch/securityanalytics/correlation/alert/CorrelationAlertService.java

@@ -26,6 +26,7 @@
 import org.opensearch.core.xcontent.NamedXContentRegistry;
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.core.xcontent.XContentParser;
+import org.opensearch.index.IndexNotFoundException;
 import org.opensearch.index.query.BoolQueryBuilder;
 import org.opensearch.index.query.QueryBuilders;
 import org.opensearch.index.query.TermsQueryBuilder;
@@ -188,7 +189,11 @@ public void getCorrelationAlerts(String ruleId, Table tableProp, ActionListener<
                 },
                 e -> {
                     log.error("Search request to fetch correlation alerts failed", e);
-                    listener.onFailure(e);
+                    if (e instanceof IndexNotFoundException) {
+                        listener.onResponse(new GetCorrelationAlertsResponse(Collections.emptyList(), 0));
+                    } else {
+                        listener.onFailure(e);
+                    }
                 }
         ));
     }