Steps to Repo:
1. Hierarchy > 3D Object > terrain
2. Terrain > pain trees > edit tree > add tree
3. Select light game object > set mode to baked
4. Window > lighting > settings > real-time lighting >uncheck real-time global illumination
5. Mixed lighting > check baked global illumination > generate lighting
6. Once baking is complete > observe the shadows are not getting baked

Frequency:
Always

Actual Result:
Tree shadows are missing after baking global illumination

Expected Result:
Tree shadows are getting baked and are visible on terrain

Environment:
Occurring on Windows and MacOS

Working with:
Unity 2017.2.0f3, Unity 2017.3.0a7

Reproducible with:
2017.3.0b1, Unity 2017.3.0b11, 2018.1.0a5