The Dropdown icon for "Contacts" properties doesn't work under the "Rigidbody 2D" component in Inspector, refer the attached video

Steps to repro:
1. Create a new project
2. Hierarchy >right-click > Create Empty
3. Inspector > Add Component > Rigidbody 2D
4. Click > Contacts expand icon

Actual Result:
"Contacts" Dropdown icon is not clickable.

Expected Result:
"Contacts" Dropdown icon should be click and expand.

Reproducible in:
2020.1.0a20, 2019.3.0f6 (b7564ae9e143), 2019.3.0a7

Working fine in:
2019.3.0a6, 2019.2.14f1

Environment:
Window 10, macOS 10.14