Feature Request: empty object for + and -

[rdpoor]

Perhaps it exists already, but it would be handy to have an ObjectSCADObject with the property that
open_scad_object + EMPTY == open_scad_object
open_scad_object - EMPTY == open_scad_object

[jeff-dh]

The closest I know of is using an empty union. The resulting object is not identical, your equal assertion will fail, but the resulting object should be the same. ```python from solid2 import * x = cube() empty = union() (x + empty).as_scad() (x - empty).as_scad() ```