[Bug] Adding shadow makes markLine disappear if the line is horizontal or vertical

[soundlake]

Version

6.0.0

Link to Minimal Reproduction

https://codepen.io/soundlake/pen/yyORLNg

Steps to Reproduce

1. Create chart with markLine
2. Add data that can produce horizontal (no height) or vertical (no width) mark line
3. Add shadow* to the lineStyle

Current Behavior

The line gets disappeared while symbols and label are shown.

Expected Behavior

The line also be shown.

Environment

- OS: Windows 11
- Browser: Edge 142
- Framework: Plain JS

Any additional comments?

It might be a zrender bug, but at least, the doc should warn.

This is a known issue for SVG, at least on StackOverflow.