Steps to repro:

1. Open attached project and 't1' scene;
2. Open Frame Debugger (Window -> Frame Debugger);
3. Expand any event that renderers SpeedTree mesh (e.g. DepthPass.Job);
5. Select any draw call under this event (e.g. Draw Mesh Conifer_Desktop_LOD0);
6. Open Preview tab of Frame Debugger window;
7. Close Unity Editor.

Expected result:
Editor closes without errors.

Actual result:

- Error: 'GetManagerFromContext: pointer to object of manager 'LightmapSettings' is NULL (table index 26)' is shown;
- Editor crashes and BugReporter pops up.

See attached video.
Regression introduced in Unity 2017.1.0b2.

- Reproducible in 2017.1.0b2;
- Not reproducible in 2017.1.0b1, 5.6.0p3, 5.6.0f3, 5.5.2p1;
- Reproducible on Windows 10 and OSX 10.12.3;
- Reproducible only for selecting SpeedTree model preview in FrameDebugger, not reproducible for simple primitive meshes.