hugegraph 备份出错

### Expected behavior 期望表现
能正常备份

### Actual behavior 实际表现
备份出错， 消息： Caused by : com .baidu.hugegraph.hugeException: Can't write json: undefined index label with id : '2320" (through reference chain" java.util.arrayList[143])

### Steps to reproduce the problem 复现步骤
1. 执行备份 命令
2. 备份报错
3

### Status of loaded data 数据状态

#### Vertex/Edge summary 数据量
< 10000

#### Vertex/Edge example 数据示例
{type something here...}

#### Schema(VertexLabel, EdgeLabel, IndexLabel) 元数据结构
{type something here...}

### Specifications of environment 环境信息
- hugegraph version: 0.10.4.0