Dropdown menu options overlap each other in `Arc Dark Contrast(Material)` theme

[rew1nter]

Describe the bug Every dropdown menu's options overlap in this theme. I'm seeing this issue in all Arc themes. Other themes are fine.

To Reproduce Steps to reproduce the behavior:

1. Click on any drop down menu after switching to the an Arc theme. (Even the customizer drop down menu gets distorted.)
2. Hover over the menu with mouse.

Screenshots

Versions Burp Suite Pro Version [2020.12.1]

Additional The more you hover over the dropdown options, more distorted those get. Its my favourite theme. Will be waiting for a fix.