message: NPE check before metrics sum
diff: @@ -64,7 +64,11 @@ public interface ClusterMapper {
  }
  default BigDecimal sumMetrics(Map<String, BigDecimal> metrics) {
  + if (metrics == null) {
  return metrics.values().stream().reduce(BigDecimal.ZERO, BigDecimal::add);
  + } else {
  + return BigDecimal.ZERO;
  + }
  }
  default Path resolvePath(String path) {
  