Clicking on the title of Padding property for Rect Mask 2D doesn't expand however it expands when clicked on the Dropdown icon
Please refer to the attached video.

Steps to repro:
1. Create a new project
2. Hierarchy >right-click > Create Empty
3. Inspector > Add Component > Rect Mask 2D
4. Click > Padding title

Actual Result:
The Dropdown list for "Padding" property doesn't open on clicking the title

Expected Result:
The dropdown list for "Padding" property should respond and open on clicking the title.

Occurring on:
2020.2.0a5

Working fine on:
2020.2.0a4, 2020.1.0b3

Environment:
Windows and Mac