When Prefab of gameobject is created and component is added on gameobject, then after undoing added component Add component button is overlapping on Default Material.

Steps to repro:
1. Create New Project
2. Hierarchy > 3D Object > Cube > Create Prefab
3. Hierarchy > Cube > shrink Box collider > Add component > Audio Source > Undo

Actual result:
Add component button is overlapping on Default Material

Expected result:
Add component button does not get overlap on Default Material

Reproducible in:
2020.2.0b4, 2020.1.6f1 , 2019.4.10f1, 2019.3.16f1

Working Fine with:
2018.4.27f1

Environment:
Occurring on Mac 10.15 only.