sfcalc: don't output (0,0,0) for SmallStructure with --dmin (#180)
sfcalc: don't output (0,0,0) for SmallStructure with --dmin (#180)

(it was never outputted for macromolecules)

project-gemmi/gemmi,project-gemmi/gemmi,project-gemmi/gemmi,project-gemmi/gemmi