Reproduction steps(GIF attached):

1. Open attached project.
2. Open "Simple_Scene" scene.
3. Go to "Window > Lighting > Scene" and click "Build".
4. Select "Plane" or "Cube" game object in the hierarchy.
5. Go to "Window > Lighting > Object" tab.
6. Click on "Preview" button if "Preview" tab is expanded.
7. Click on "Charting" button.
8. Select "Baked Intensity" or "Baked Direction".
9. Notice:
* Lightmap object preview doesn't show up.
* Inspector and Lighting tabs gets unresponsive.
* Console is flooded with:

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.LightingWindowObjectTab.ObjectPreview (Rect r) (at C:/buildslave/unity/build/Editor/Mono/SceneModeWindows/LightingWindowObjectTab.cs:185)
UnityEditor.LightingWindow.PreviewSection () (at C:/buildslave/unity/build/Editor/Mono/SceneModeWindows/LightingWindow.cs:291)
UnityEditor.LightingWindow.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneModeWindows/LightingWindow.cs:245)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)

Regression introduced in: 5.4.0b4