Left button scroll blocks clicking on empty area from taking focus

[bootleq]

Describe the bug
With scrolling with Left mouse button, user can no longer put focus to a element by "clicking" its blank area.

Steps To Reproduce
Steps to reproduce the behavior:

1. Go to add-on options page, use the side panel to test.
2. Click on blank area (where no text is there), like first red point in the screenshot.
3. Hit keyboard Down button.
4. The problem is that, the scroll container doesn't scroll.

Expected behavior
When click, the focus should be made to the scroll container, and then a "Down" key hitting should make the scroll moving down.
Like when we click on some "text" (second red point in screenshot), the behavior works normally.

Device info:

• operating system: Windows 10 22H2
• Browser and version: Firefox 132.0.2
• addon version: 9.2