🐛 [BUG]分组柱状图，只有一组的情况下显示异常

### 🐛 Bug description [分组柱状图，只有一组的情况下显示异常]

- https://codesandbox.io/s/g2plot-issue-template-forked-fikvrn

### 📷 Step to reproduce
- 分组柱状图，数据data只有一组的情况
- options设置，dodgePadding: 0
- 柱状图无法显示

### 🏞 Expected result

### 🚑 Any additional [like screenshots]

* **G2Plot Version**: 2.3.35
* **Platform**: chrome

Start with the linked CodeSandbox reproduction and verify the behavior in Chrome using G2Plot 2.3.35. Exercise a grouped bar chart with one data group and dodgePadding set to 0; done means the bars render as shown in the expected-result image.

Written by the indexing model from the issue text.