Steps to repro:
1. Open the attached project 'case_886275-Progressive_Lightmapper_Adventure_Game' and 'ProgressiveLightmappingExample' scene;
2. In the Lighting window select Clear Baked Data;
3. In the Lighting window set Lightmapper to Progressive CPU;
4. In the Lighting window press Generate Lighting button;
5. Wait until the Lighting is baked;
6. In the Lighting window change Lightmapper to Progressive GPU;
7. In the Lighting window press Generate Lighting button;
8. Wait until the Lighting is baked;
9. In the context menu select File>New Scene;
10. If the prompt menu appears, click Save;
11. When the new scene is opened in the Lighting window press Generate Lighting button.

Actual result:
Editor crashes. See attached video.
Last calls from the stacktrace:
0x00007ff6c45f09e1 (Unity) Enlighten::CpuUpdateManager::UpdateGpuTextures
0x00007ff6c45f02c6 (Unity) Enlighten::CpuUpdateManager::Update
0x00007ff6c0935e19 (Unity) EnlightenRuntimeManager::Update
0x00007ff6c335249d (Unity) gi::PostUpdate
0x00007ff6c337e2f0 (Unity) GISceneManager::Update

Regression introduced in Version 2019.1.0.

Expected result:
Editor doesn't crash.

Notes:
- Reproducible in 2020.2.0a013, 2020.1.0b9, 2019.3.15f1, 2019.2.21f1, 2019.1.14f1;
- Not reproducible in Version 2018.4.23f1;
- Reproducible on Windows 10;
- This case was masked under the case 1244384; it's still reproducible now when 1244384 is fixed;
- Only reproducible when Realtime GI is enabled together with the Baked GI.