How to reproduce:
1. Open a new project
2. Create a Terrain in the Scene
3. Add a texture to the Terrain
4. Enter the Play mode

Expected result: Editor enters Play mode without freezing or causing Scene window to turn black.
Actual result: Editor freezes, the Scene window turns black.

Reproducible with - 2018.2.0x-ImprovedPrefabs (ff19e2e229d2)
Not reproducible with - 2017.1.4p2, 2017.2.3p2, 2017.4.7f1, 2018.1.9f1, 2018.2.0f2, 2018.3.0a5

Notes:
- The issue occurs when entering Play mode during the baking process, as well as afterwards.
- The issue does not occur if the scene is saved before entering Play mode (after the baking process finishes, or Editor is restarted).