Clicking on the title of Particle system window doesn't Minimize and Maximize however it works when clicked on the Dropdown icon
Please refer to the attached video.

Steps to repro:
1. Create a new project
2. Hierarchy >right-click > Effects > Particle System.
3. Click > Particle System title

Actual Result:
Particle system window doesn't Minimize and Maximize clicking on the title

Expected Result:
Particle system window Minimize and Maximize Properly clicking on the title

Occurring on:
2020.2.0a5

Working fine on:
2020.2.0a4, 2020.1.0b3

Environment:
Windows and Mac