Steps to repro:
1. Open the attached project and 'ProgressiveLightmapperExample' scene;
2. Ensure that the Light Explorer window is active (if not, open it via Window>Rendering>Light Explorer);
3. In context menu select File>New scene.

Expected result:
The new scene is being opened without errors in the console.

Actual result:
Error:
"NullReferenceException: Object reference not set to an instance of an object
UnityEditor.EditorGUI+EnumNamesCache.GetEnumLocalizedGUIContents (UnityEditor.SerializedProperty property) (at /Users/builduser/buildslave/unity/build/Editor/Mono/EditorGUI.cs:7872)"

Reproducible with: 2019.3.5f1, 2019.3.13f1, 2020.1.0b8,2020.2.0a11
Not reproducible with: 2018.4.21f1, 2019.1.14f1, 2019.2.21f1, 2019.3.4f1

Notes:
- Reproducible on Windows and OSX;
- The issue is only reproducible when the Light Explorer window is active (shown in the Editor layout).