Material Preview for Post Process Material Does not display in Material Editor

In the Material editor for when working with a Post Process Material, the material does not appear in the preview window.

Regression:
This issue does not occur in 4.15.2 Binary Builds

1. Create a new project (No template or starter content needed)
2. create a new material > name it TEST_MAT > Open TEST_MAT
3. add a constant 1 to the material graph and connect it to the Emissive Color option (expected Result)
4. Change the Material Domain to Post Process
5. Click the Apply button
   Result: The Material does not appear in the Material Preview window
   Expected Result: The Material appears in the Material Preview window