output: #fixed code
                               @Override
  	public RegistryCenterConfiguration findConfigByNamespace(String namespace) {
  		if(Strings.isNullOrEmpty(namespace)){
  			return null;
  		}
  		Collection<ZkCluster> zkClusters = RegistryCenterServiceImpl.ZKADDR_TO_ZKCLUSTER_MAP.values();
  		for (ZkCluster zkCluster: zkClusters) {
  			for(RegistryCenterConfiguration each: zkCluster.getRegCenterConfList()) {
  				if (each != null && namespace.equals(each.getNamespace())) {
  					return each;
  				}
  			}
  		}
  		return null;
  	}
input: #vulnerable code 
                               @Override
  	public RegistryCenterConfiguration findConfigByNamespace(String namespace) {
  		if(Strings.isNullOrEmpty(namespace)){
  			return null;
  		}
  		Collection<ZkCluster> zkClusters = RegistryCenterServiceImpl.ZKADDR_TO_ZKCLUSTER_MAP.values();
  		for (ZkCluster zkCluster: zkClusters) {
  			for(RegistryCenterConfiguration each: REGISTRY_CENTER_CONFIGURATION_MAP.get(zkCluster.getZkAddr())) {
  				if (each != null && namespace.equals(each.getNamespace())) {
  					return each;
  				}
  			}
  		}
  		return null;
  	} 
                              #location 8 
                              #vulnerability type NULL_DEREFERENCE