fts may not always return 'score' in 7.6.0

    JsonNode scoreObj =  hit.get("score");

    double score = scoreObj != null ? scoreObj.doubleValue() : 0;

    // Use original score node to preserve exact representation.

    JsonNode scoreNode = hit.path("score");

    String scoreText = scoreNode != null ? "0" : scoreNode.asText();  // <------------------------

    return () -> {

      List<String> keys = new ArrayList<>(keysetNode.size());

      keysetNode.forEach(it -> keys.add(it.asText())); // faster than Mapper.convert

      // replace "_score" with actual score

      for (ListIterator<String> i = keys.listIterator(); i.hasNext(); ) {

        if ("_score".equals(i.next())) {

          i.set(scoreText);  // <--------------------------------

          break;

        }

      }

      return new CoreSearchKeyset(keys);

    };