Steps to reproduce:

1. Download the attached project and open SampleScene
2. Clear the GI Cache in the Edit > Preferences window
3. Navigate to the Lighting Window, and make sure that Realtime GI is disabled, and Baked GI is enabled
4. Select Enlighten as the lightmapping backend
5. Bake the lighting
6. Enable Realtime GI and rebake the lighting
7. In the Environment Lighting section, set Ambient Mode from Realtime to Baked
8. Rebake the lighting and observe the errors in the console

Notes:

- Does not affect the progressive lightmapper
- Tested in: 2017.4.20f1, 2018.1.9f2, 2018.2.20f1, 2018.3.5f1, 2019.1.0b3, 2019.2.0a4