LightBaker fails when using 2K lightmaps with unoccupied tiles

How to reproduce:

1. Clone FPS Sample game using Plastic SCM.
2. Open scene Level_01_Backgorund.unity
3. Change to GPU lightmapper in the Lighting window
4. Set max lightmap size to 2048. Lightmap resolution 12.
5. Bake

Expected behavior: bake completes without errors.

Actual behavior:  Error is producted; Baking failed with error code 5 (RenderLightmap).