output: #fixed code
                                  public static void startNamespaceShardingManagerList(int count) throws Exception {
          assertThat(nestedZkUtils.isStarted());
          for (int i = 0; i < count; i++) {
              ZookeeperRegistryCenter shardingRegCenter = new ZookeeperRegistryCenter(new ZookeeperConfiguration(-1, nestedZkUtils.getZkString(), NAMESPACE, 1000, 3000, 3));
              shardingRegCenter.init();
              NamespaceShardingManager namespaceShardingManager = new NamespaceShardingManager((CuratorFramework) shardingRegCenter.getRawClient(),NAMESPACE, "127.0.0.1-" + i);
              namespaceShardingManager.start();
              namespaceShardingManagerList.add(namespaceShardingManager);
          }
      }
input: #vulnerable code 
                                  public static void startNamespaceShardingManagerList(int count) throws Exception {
          assertThat(nestedZkUtils.isStarted());
          for (int i = 0; i < count; i++) {
              shardingRegCenter = new ZookeeperRegistryCenter(new ZookeeperConfiguration(-1, nestedZkUtils.getZkString(), NAMESPACE, 1000, 3000, 3));
              shardingRegCenter.init();
              NamespaceShardingManager namespaceShardingManager = new NamespaceShardingManager((CuratorFramework) shardingRegCenter.getRawClient(),NAMESPACE, "127.0.0.1-" + i);
              namespaceShardingManager.start();
              namespaceShardingManagerList.add(namespaceShardingManager);
          }
      } 
                              #location 6 
                              #vulnerability type NULL_DEREFERENCE