[Bug Report]summary 行处理 type: 'index' 行出现异常

[WeijianXu]

Environment

window10 / chrome100.0.4896.127 / Vue 2.6.14

Reproduction link

https://run.iviewui.com/BMyU0azc

Steps to reproduce

1. 设置序号列 type: 'index';
2. 自定义 summary-method，数据中无序号列（因为没有 key）;

What is expected?

总计行正常显示

What is actually happening?

报错：TypeError: Cannot read properties of undefined (reading 'value')

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排查发现：序号列没有 key，导致 column.key 获取失败