Details panel is blank when compiling after setting default subobject property to None

If the user sets a default subobject property to None, the Details panel for the component will be completely blank and not able to restore the subobject property in anyway.

1. Download and extract the attached project.
2. Generate project files, build and open it in editor.
3. Open TestActor.
4. Expand to the full blueprint editor..
5. Select TestComp.
6. In the Details panel, set the subobject property to None.
7. Compile.

RESULT

The Details property is completely blank, even missing the subobject property.

EXPECTED

Either for the subobject property to remain, or something to prevent a destructive action like this.