Caused by f98b01e492
The issue of uninitialized `Editing` (in new scenes) has come up before,
see e.g. https://projects.blender.org/blender/blender/issues/
118633#issuecomment-1134447
So it is not uncommon to guard against `Editing` being null, same is now
done here
Pull Request: https://projects.blender.org/blender/blender/pulls/135623