[Bug] Shadow properties like `shadowBlur` removes the line on the SVG graph

[JeromeDeLeon]

Version

5.2.2

Link to Minimal Reproduction

https://codesandbox.io/s/smoothed-line-chart-forked-fsv8pp?file=/index.js

Steps to Reproduce

1. Open the link to minimal reproduction
2. See the comment there

Current Behavior

The SVG graph hides the line when the series.data have all the same value and when it has shadow* properties like shadowBlur

Expected Behavior

The SVG graph should display the line when the series.data have all the same value and when it has shadow* properties like shadowBlur

Environment

- OS: Windows 10
- Browser: MS Edge 104.0.1293.47

Any additional comments?

It works when using the canvas as the renderer

[plainheart]

This is a known issue. See also ecomfe/zrender#792