When "Lighting Data Asset" is set to none, Baked Lightmaps Preview doesn't disappear, also if LightingData is set into "Lighting Data Asset" Baked Lightmaps preview doesn't appear, refer the attached video.

Note: On entering play mode Baked Lightmaps Preview update according to Lighting Data Asset is set or None

Steps to repro:
1. Create a new project
2. Hierarchy > Create > 3D Object > Terrain
3. Window > Rendering > lighting > Generate Lighting
4. Baked Lightmaps > Lighting Data Asset > None
5. Baked Lightmaps > Lighting Data Asset > LightingData

Actual Result:
Baked Lightmaps Preview is not updating real-time when Lighting Data Asset is set to None

Expected Result:
Baked Lightmaps Preview should be disappeared when Lighting Data Asset is set to None

Occurring on:
2020.2.0a18. 2020.1.0b16, 2019.3.15f1, 2019.2.13f1, 2019.1.11f1, 2018.4.24f1

Environment:
Occurring on Windows 10 & macOS 10.15