Steps to repro:

1. Open attached project and 't1' scene;
2. Select 'Broadleaf_Desktop' prefab in the Hierarchy;
3. In the Inspector select any LOD level (e.g. LOD 0);
4. Observe SpeedTree preview.

Expected result:
Speedtree preview is rendered for selected Speedtree prefab LOD level (see attached expected.png).

Actual result:
Speedtree preview is not shown for selected Speedtree prefab LOD level (see attached actual.png).

Regression introduced in Unity 2017.1.0.

Notes:
- Reproducible in Unity 2017.1.0b6;
- Not reproducible in Unity 5.6.1p1;
- Reproducible on Windows 10 and OSX 10.12.3.