Steps to repro:

1. Open attached project and 't1' scene on Windows;
2. In the Project folder go to 'Free_SpeedTrees' folder;
3. Drag 'Broadleaf_Desktop' prefab to the Scene view.

Actual result:
Editor crashes. See attached video.

The callstack shows following error:
GetManagerFromContext: pointer to object of manager 'RenderSettings' is NULL (table index 25)
UnityEngine.RenderSettings:get_fog()
UnityEditor.SceneView:SetupFogAndShadowDistance(Boolean&, Single&) (at C:\buildslave\unity\build\Editor\Mono\SceneView\SceneView.cs:861)
UnityEditor.SceneView:OnGUI() (at C:\buildslave\unity\build\Editor\Mono\SceneView\SceneView.cs:1502)
System.Reflection.MonoMethod:InternalInvoke(Object, Object[], Exception&)
System.Reflection.MonoMethod:Invoke(Object, BindingFlags, Binder, Object[], CultureInfo) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
System.Reflection.MethodBase:Invoke(Object, Object[]) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.HostView:Invoke(String, Object) (at C:\buildslave\unity\build\Editor\Mono\HostView.cs:272)
UnityEditor.HostView:Invoke(String) (at C:\buildslave\unity\build\Editor\Mono\HostView.cs:265)
UnityEditor.HostView:InvokeOnGUI(Rect) (at C:\buildslave\unity\build\Editor\Mono\HostView.cs:232)
UnityEditor.DockArea:OldOnGUI() (at C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:407)
UnityEngine.Experimental.UIElements.IMGUIContainer:DoOnGUI(Event) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\IMGUIContainer.cs:115)
UnityEngine.Experimental.UIElements.IMGUIContainer:HandleEvent(Event, VisualElement) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\IMGUIContainer.cs:185)
UnityEngine.Experimental.UIElements.IMGUIContainer:DoRepaint(IStylePainter) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\IMGUIContainer.cs:38)
UnityEngine.Experimental.UIElements.Panel:PaintSubTree(Event, VisualElement, Matrix4x4, Rect) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\Panel.cs:425)
UnityEngine.Experimental.UIElements.Panel:PaintSubTree(Event, VisualElement, Matrix4x4, Rect) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\Panel.cs:435)
UnityEngine.Experimental.UIElements.Panel:Repaint(Event) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\Panel.cs:450)
UnityEngine.Experimental.UIElements.UIElementsUtility:DoDispatch(BaseVisualElementPanel) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\UIElementsUtility.cs:178)
UnityEngine.Experimental.UIElements.UIElementsUtility:ProcessEvent(Int32, IntPtr) (at C:\buildslave\unity\build\Runtime\UIElements\Managed\UIElementsUtility.cs:71)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr) (at C:\buildslave\unity\build\Runtime\IMGUI\Managed\GUIUtility.cs:186)

Regression introduced in 2017.1.0f1.

Expected result:
Editor should not crash. Tree prefab instance should appear in the Hiararchy view.

Notes:
- Reproducible in 2017.1.0f1;
- Not reproducible in 2017.2.0b1, 2017.1.0b10, 5.6.1.p2;
- Reproducible only on Windows 10 (DX11); not reproducible on OSX 10.12.5 (GlCore);
- Reproducible only for tree prefabs which materials were previously re-generated.