Show warning when Insert SMILES (or other) leaves atoms at 0,0,0

[ghutchis]

Sometimes if Open Babel gen3d fails, Insert SMILES will yield all the atoms at 0,0,0

We should pop up a warning to explain this.

[matterhorn103]

Does Open Babel first generate a 2D representation and then 3-dimensionalize it in two separate steps? If so wouldn't it make sense to at least return the 2D geom when gen3d fails?

[ghutchis]

No, it's separate code. Failing the 3D coordinate generation is pretty rare, but one of my students had it happen, so we should at least have a check / warning for that case.