How to reproduce
1. Create a new project
2. Add a cube to the scene (make sure that it has mesh renderer with a material already)
3. Create new material
4. Select cube, drag a material (like 'New Material') into the 'Materials' of the MeshRenderer, but not onto the previous material
5. Observe the error message: "ArgumentException: GUILayout: Mismatched LayoutGroup.DragPerform"
6. Select cube again, and in its mesh renderer-> size type 0
7. Drag a material (like 'New Material') into the 'Materials' of the MeshRenderer
8. Undo (Ctrl+Z)-> Redo (Ctrl+Y)
9. Observe that the connection to the material is broken now.