When Two Column Layout is set then on the shrinking Project window it gets overlapped with Assets window. Refer attached video

Steps to Repro:
1. Create a new Project
2. Project Window > Set Two Column Layout
3. Drag and shrink Project Window

Actual Result:
The project window is overlapping with the Assets window when they are shrunk.

Expected Result:
Project and Assets window should maintain their position after shrinking.

Reproducible on:
2021.2.0a12, 2021.2.a10

Working Fine with:
2021.2.0a9, 2021.1.2f1, 2020.3.3f1, 2020.2.6f1, 2020.1.17f1, 2019.4.22f1

Environment:
Occurring on macOS and Windows 10