Fatal Error "GetManagerFromContext: 'Lightmap Settings' is NULL" is thrown after selecting any material, locking Inspector, and then closing the Editor.

To reproduce:
1. Create a new project
2. Create a new material and select it
3. Lock the Inspector window where the material is assigned to
4. Press "X" in Editor title-bar to quit

Desired outcome: The editor closes without a crash.
Actual result: Editor shows "GetManagerFromContext: pointer to object of manager "Lightmap Settings" is NULL (table index 26) UnityEditor.Material:OnDisable()" then crashes after pressing "Quit" button.

Stack trace:
GetManagerFromContext: pointer to object of manager 'LightmapSettings' is NULL (table index 26)
UnityEditor.SceneManagement.EditorSceneManager:INTERNAL_CALL_ClosePreviewScene(Scene&)
UnityEditor.SceneManagement.EditorSceneManager:ClosePreviewScene(Scene)
UnityEditor.PreviewScene:Dispose()
UnityEditor.PreviewRenderUtility:Cleanup()
UnityEditor.MaterialEditor:OnDisable()

Reproduced with 2017.1.0b2, 2017.1.0f1, 2017.2.0a1, 2017.2.0b1
Not reproduced with 5.5.4p1, 5.6.2p1, 2017.1.0a1, 2017.1.0a4, 2017.1.0b1
Regression introduced in 2017.1.0b2