Reproduction steps:
1. Open the attached project "ReproProj"
2. Open the “/Assets/Scenes/SampleScene.unity” Scene
3. In Hierarchy, select the “Directional Light” GameObject
4. Observe the Console window

Expected result: No errors are present
Actual result: Error “NullReferenceException: Object reference not set to an instance of an object“ is spammed

Reproducible with: 7.0.0-exp.3 (2022.2.16f1), 7.0.0 (2021.3.35f1, 2022.3.20f1, 2023.2.12f1, 2023.3.0b9)
Not reproducible with: 6.4.2-preview.2 (2022.2.16f1)

Reproducible on: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested

Workaround:
In MLSpatialMapper.cs (Packages/com.unity.xr.magicleap/Runtime/Meshing/MLSpatialMapper.cs), change line:
{{m_MeshType = this.serializedObject.FindProperty("m_MeshType"); }}
to:
{{m_MeshType = this.serializedObject.FindProperty("m_RequestedMeshType");}}