Black window appears on expanding Particle Overlay when it docked, Refer to the attached video

Steps to Reproduce:
1. Create a New Project
2. Hierarchy > Right-Click > Effects > Particle System
3. Scene View > Drag and Dock Particle Overlay window.
4. Scene View > Particle Overlay window > Click expand icon

Actual result:
Expanding Particle Overlay window appears black when its docked

Expected result:
A particle Overlay window appears gracefully

Occurring on:
2021.2.0a17

Note: New scene view overlays feature is Introduce in 2021.2.0a17

Environment:
Ubuntu 18.04 LTS