slave with requires could not raise

tiramisu/option/masterslave.py

@@ -230,10 +230,13 @@ class MasterSlaves(object):
                         multi.append_properties_error(value)
                     else:
                         return value
-                else:
+                elif index is None:
                     multi.append(value, setitem=False, force=True, validate=validate,
                                  force_permissive=force_permissive)
                     one_has_value = True
+                else:
+                    multi = value
+                    one_has_value = True
             if not one_has_value:
                 #raise last err
                 if returns_raise: