Rays propagating after missing a surface, intended?

in the example "grating_examples", martinez.opm, several rays miss the second surface of the lens because the curved surface lies in front of the previous plane surface (no aperture defined).

the function rays.refract_on_surface() correctly marks them as "missed a surface", but shouldn't the underlying function ray.refract_on_surface() set the missed rays to invalid? Because right now, the rays are still propagating and hit the grating