Fix DLQ writer writing empty list (opensearch-project#2931)

Signed-off-by: Krishna Kondaka <krishkdk@dev-dsk-krishkdk-2c-bd29c437.us-west-2.amazon.com>
Co-authored-by: Krishna Kondaka <krishkdk@dev-dsk-krishkdk-2c-bd29c437.us-west-2.amazon.com>

Author: kkondaka

data-prepper-plugins/opensearch/src/main/java/org/opensearch/dataprepper/plugins/sink/opensearch/BulkRetryStrategy.java

@@ -258,6 +258,10 @@ private void handleFailures(final AccumulatingBulkRequest<BulkOperationWrapper,
 
     private BulkOperationRequestResponse handleRetry(final AccumulatingBulkRequest request, final BulkResponse response, int retryCount) throws InterruptedException {
         final AccumulatingBulkRequest<BulkOperationWrapper, BulkRequest> bulkRequestForRetry = createBulkRequestForRetry(request, response);
+        if (bulkRequestForRetry.getOperationsCount() == 0) {
+            return null;
+        }
+
         final BulkResponse bulkResponse;
         try {
             bulkResponse = requestFunction.apply(bulkRequestForRetry);