Actions window has no background panel and border which results in overlapping of text on other windows

Steps to repro:
1. Create a new project.
2. Install "ProBuilder" package from Window > Package Manager.
3. Tools > ProBuilder > ProBuilder Window
4. Create a New Shape
5. Select face of newly created shape using "Face Selection Tool"
6. Open UV Editor from ProBuilder window

Actual Result:
Background panel and the border is missing for "Actions" window in the UV Editor window

Expected Result:
Action window appears with background panel and border

Occurring in: 2019.3.0a11, 2019.3.0a3

Working fine in:
2019.3.0a2, 2019.2.0f1

Package version occurring: 4.1.0, 4.0.2

Environment:
Windows 10 and macOS 10.14.

Note: Refer attached screenshot