execute item failure callback execution on bulk request error

opensearchutil/bulk_indexer.go

@@ -503,9 +503,7 @@ func (w *worker) flush(ctx context.Context) error {
 
 	blk, err = w.bi.config.Client.Bulk(ctx, req)
 	if err != nil {
-		if err != nil {
-			return w.handleBulkError(ctx, fmt.Errorf("flush: %w", err))
-		}
+		return w.handleBulkError(ctx, fmt.Errorf("flush: %w", err))
 	}
 
 	for i, blkItem := range blk.Items {
@@ -518,7 +516,7 @@ func (w *worker) flush(ctx context.Context) error {
 		item = w.items[i]
 		// The OpenSearch bulk response contains an array of maps like this:
 		//   [ { "index": { ... } }, { "create": { ... } }, ... ]
-		// We range over the map, to set the first key and value as "op" and "info".
+		// We range over the map, to set the last key and value as "op" and "info".
 		for k, v := range blkItem {
 			op = k
 			info = v