[Bug] Sankey breaks when there is a loop or a cycle

### Version

5.4.3

### Link to Minimal Reproduction

https://echarts.apache.org/examples/en/editor.html?c=sankey-itemstyle

### Steps to Reproduce

go to https://echarts.apache.org/examples/en/editor.html?c=sankey-itemstyle
change data set so that one of the data items loops back to the first entry and the sankey breaks

### Current Behavior

the sankey does not load

### Expected Behavior

the sankey load and where the data loops back my expectation is there is a line that shows the flow going back to a previous node

### Environment

```markdown
- OS: mac
- Browser: chrome
- Framework: i'm just using the website https://echarts.apache.org/examples/en/editor.html?c=sankey-itemstyle
```

### Any additional comments?

_No response_