#vulnerable code 
                                @Override
    public Instance selectOneHealthyInstance(String serviceName, List<String> clusters, boolean subscribe)
        throws NacosException {

        if (subscribe) {
            return Balancer.RandomByWeight.selectHost(
                hostReactor.getServiceInfo(serviceName, StringUtils.join(clusters, ",")));
        } else {
            return Balancer.RandomByWeight.selectHost(
                hostReactor.getServiceInfoDirectlyFromServer(serviceName, StringUtils.join(clusters, ",")));
        }
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public Instance selectOneHealthyInstance(String serviceName, List<String> clusters, boolean subscribe)
        throws NacosException {
        return selectOneHealthyInstance(serviceName, Constants.DEFAULT_GROUP, clusters, subscribe);
    }