Sidebar selected item's text unreadable under light mode

[ys-chung]

Before opening your issue, please make sure you answer YES to all of the questions below.

• Are you running the latest version of the app?
• Are you running a release, stable version of macOS?
• Have you looked at previous issues to see if you're having an issue that's already being worked on?
• If your issue is about compilation or project setup, have you followed the instructions from the readme?
• Have you read the Code of Conduct, and will you uphold it's values?

If you answered YES to all of the questions, please provide as much information as possible about your issue.

• Version of macOS
  • 10.14.5
• Version of the app
  • 6.1.2
• What were you trying to do when the issue happened
  • I opened the app under light mode, and the background colour of the selected item in the sidebar appears too light to read the text.
• If it is a wrong behavior, list all steps required to reproduce it
  1. Switch to light mode
  2. Open the app
• Please add screenshots if you think they might help us diagnose the issue

[mediter]

Similar to #527

[insidegui]

Closing this as a duplicate of #527