[UI] Sprites are not getting rendered when set in dropdown options list

Steps to Reproduce:
1. Create a new unity project.
2. Import any image and set texture type to Sprite(2D and UI).
3. Hierarchy >> UI >> Dropdown.
4. Select dropdown object from the hierarchy.
5. Assign sprite to options from dropdown component.
6. Enter play mode.
7. Click on dropdown created in "Game view".
8. Observe that sprite is not rendering.

Environment:
Occurring on both Windows and Mac.

Occuring With:
2018.1.0b8, 2017.3.1p2 , 2017.3.0f3, 2017.2.0f3, 2017.1.0f3, 5.6.0f3