In Particle Effects window Simulate layer Dropdown options are not getting selected.

Steps to repro:
1. Create a new project.
2. Hierarchy >Effects > Particle System
3. Select any option in Dropdown list.

Actual Result:
Unable to select any option in Simulate Layers Dropdown in Particle effects window

Expected Result:
Simulate Layers Dropdown options is selectable.

Reproducible in:
2020.2.0a7, 2020.1.0b6, 2020.1.0a26

Working fine in:
2020.1.0a25

Environment: occurs only on mac 10.15