Drop down arrow to collapse a component is missing from the sorting group component

Steps to Repo:
1. Hierarchy > right click > 2D Object > add Sprite game object
2. Select sprite game object > inspector window > add component > add 'Sorting Group' component
3. Observe that drop down arrow icon doesn't appear for sorting group component.

Frequency:
Always

Actual Result:
Drop down arrow icon doesn't appear for sorting group component.

Expected Result:
Drop down arrow icon should appear for sorting group component.

Environment:
Occurring on Windows and MacOS

Reproducible with:
Unity 2018.1.0a6, 2017.3.0f1, 2017.2.0f3, 2017.1.2f1, 5.6.4p3