fix charge handling in make sample molecule

Author: mjohnson541

rmgpy/molecule/group.py

@@ -2957,7 +2957,7 @@ def make_sample_molecule(self):
                                     'S0sc', 'S2sc', 'S2dc', 'S2tc', 'S4sc', 'S4dc', 'S4tdc', 'S6sc', 'S6dc', 'S6tdc']
                 if group_atom.atomtype[0] in [ATOMTYPES[x] for x in positive_charged] and atom.charge > 0:
                     pass
-                elif atom.charge in group_atom.charge:
+                elif atom.charge in group_atom.atomtype[0].charge:
                     # declared charge in original group is same as new charge
                     pass
                 else: