Indent lines was not visible

[Arcadi4]

Describe the bug
The indent lines for tree views outside the editor use the same color as the background.

To Reproduce
Steps to reproduce the behavior:

1. Turn on indent lines at Appearance & Behaviour > Appearance > Tree Views > Show indent guides

Screenshots

As the screenshot shows, the lines weren't visible:

A screenshot of the default dark theme in contrast:

Application:
WebStorm