Steps to repro:
1. Open the attached project and 'ProgressiveLightmappingExample' scene;
2. In the Lighting window press 'Generate Lighting' button.

Expected result:
Lighting is baked without errors.

Actual result:
Following error is shown:

"Selected texture format 'ARGB 16 bit' for platform 'DefaultTexturePlatform' is not valid with the current texture type 'Default'.
0x00007FF6AE31C23C (Unity) StackWalker::GetCurrentCallstack
0x00007FF6AE31F711 (Unity) StackWalker::ShowCallstack
0x00007FF6ACBCF035 (Unity) GetStacktrace
0x00007FF6AEEBC27D (Unity) DebugStringToFile
0x00007FF6AC4383F3 (Unity) TextureImporter::CheckTextureFormatValue
0x00007FF6AC44ACBF (Unity) TextureImporter::SetPlatformTextureSettings
0x00007FF6AEC281BF (Unity) SetTextureImporterSettings
0x00007FF6AEC2690E (Unity) MoveTextureSnapshotsToAssetsFolder
0x00007FF6AEC25328 (Unity) WriteLightingDataAssetJob::Integrate
0x00007FF6AC7EEC16 (Unity) JobManager::IntegrateCompletedJobs
0x00007FF6AEB944D4 (Unity) GISceneManager::Update
0x00007FF6AEB914B5 (Unity) `GISceneManager::GISceneManager'::`2'::tickGIInEditorRegistrator::Forward
0x00007FF6ABBC5419 (Unity) CallbackArray::Invoke
0x00007FF6AC3487EF (Unity) ProfilerCallbackInvoke<CallbackArray,281736>::Invoke
0x00007FF6AC354923 (Unity) Application::TickTimer
0x00007FF6ACBD6555 (Unity) MainMessageLoop
0x00007FF6ACBD8F8F (Unity) WinMain
0x00007FF6AF855512 (Unity) __scrt_common_main_seh
0x00007FFBF7FC3034 (KERNEL32) BaseThreadInitThunk
0x00007FFBFA9B1471 (ntdll) RtlUserThreadStart"
See attached vide and Editor.log.

Regression introduced in 2019.2.0a11.

Notes:
- Reproducible in 2019.3.0a1. 2019.2.0a11, 2019.2.0a11;
- Not reproducible in 2019.2.0a10, 2019.1.0f1,
- Reproducible on Windows and OSX;
- Reproducible when baking lighting manually; not reproducible when auto-baking lighting;
- Reproducible only with Shadowmask light mode; not reproducible with Subtractive and Baked Indirect.
- Reproducible when baking with either CPU and GPU PLM and Enlighten.