Don't set missing default value to False

False is not always a good valid value for the field, so it is better to let the
field dealing with default value.

issue3643
review3281002
(transplanted from 9a16381241f48ca880e7544edeef54c255c99255)

tryton/gui/window/view_form/model/group.py

@@ -398,9 +398,6 @@ class Group(SignalEvent, list):
                     to_add.keys(), main_iteration=False, context=self.context)
             except RPCException:
                 return False
-            for name in to_add:
-                if name not in values:
-                    values[name] = False
             for record in new:
                 record.set_default(values, signal=signal)