[Bug] Line Charts do not work when lte is set to null

### Version

5.3.3

### Link to Minimal Reproduction

https://echarts.apache.org/examples/en/editor.html?c=line-simple&code=PYBwLglsB2AEC8sDeAoWsCeBBAHhAzgFywDaa6y5FsYGIApsQOQBuAhgDYCu9TANFVgBfcgF0B6HLgLEy1VNXS0GzAMZsw9AObAAThn6CR6ceQ7b60ACbEFFfAAtgAd2IAzTvnrkhE2Ft0IG2RfcjBgYA5IEFtQ9C9A-iJSQTtqZUZYJg4IaF4_amg2AFtMphBdYDcIMENqY1hTdCsNNi8wWVTBZohS6HwoftkmDHo2XX4siqqapibFfGAuXVVMuUV0NI3MMd1mACYABgBGQ7rt9HLK6triU8OCxTjtrY3R8YOT4_OLq5nb2BHB7dCjPDavRTvPZZI7HfY_bZ_G5MO4AVmBFzBigh1Chn2OAGYERskbNiATDhjtg1qKIjGI_CwCFxOABZNgxSjUEAQeirZLreQg9BaTTEKkbKKZaBcDgcR7UVSRPTMABG3F4IJpjUe4U5p0eel50A6WScgQAXjAwJwEeY3KamKsTfQJn4REIANxAA

### Steps to Reproduce

[Line Chart] - Set `visualMap.pieces[].lte` to `null`

### Current Behavior

Uncaught TypeError: Cannot read properties of undefined (reading 'coord')

### Expected Behavior

Color should applied from 0 to max value.

### Environment

```markdown
- OS:
- Browser:
- Framework:
```

### Any additional comments?

_No response_