Merge pull request #59 from mrjoness/pdbbuilder_fix

Replace sum with all-zero atom check for [0, 0, 0] padding. 
A future release of SidechainNet will utilize `nan` based padding.

sidechainnet/structure/PdbBuilder.py

@@ -108,7 +108,7 @@ def _get_lines_for_residue(self,
         residue_lines = []
         for atom_name, atom_coord in zip(atom_names, coords):
             if (atom_name == "PAD" or np.isnan(atom_coord).sum() > 0 or
-                    atom_coord.sum() == 0):
+                    np.all(atom_coord == 0):
                 continue
             residue_lines.append(self._get_line_for_atom(res_name, atom_name, atom_coord))
             self.atom_nbr += 1