"Register Undo object is not a ScriptableObject" when moving the sprite's pivot in Sprite Editor after exiting Play

See gif below

1. Import any sprite
2. Open sprite in Sprite Editor
3. Press Play, exit Play
4. In Sprite Editor, move the sprite's pivot

Expected result: No errors shown
Actual result: Following error is shown

Register Undo object is not a ScriptableObject
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Occurring on: 5.6.0a6 onwards up to 2017.1.0b2 (current latest)
Not occurring: 5.6.0a5 and older