Sidebar scrolling thumb is not always visible when hideOnScroll = false

[krillboi]

🐛 Bug Report

The sidebar has some problems with scrolling when hideOnScroll = false. The scrolling thumb is only partially visible when scrolled to top, as it is hidden by the NavBar. If the sidebar content is long enough, the thumb can disappear completely behind the NavBar.

Have you read the Contributing Guidelines on issues?

Yes.

To Reproduce

1. Go to our documentation site: support.touchgfx.com
2. Expand enough categories in the sidebar such that the scrollbar appears
3. Part of the scrollbar is now hidden behind the NavBar.

Expected behavior

I expect to see the whole scrollbar when scrolled all the way to the top in the sidebar and on the page.

Actual Behavior

Part of the scrollbar is hidden. The whole scrollbar is hidden if the content of the sidebar is long enough.

Your Environment

• Docusaurus version used: v. 2.0.0-alpha.50
• Version 78.0.3904.97 (Official Build) (32-bit)