Support default value.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@12979 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Form/DurationField.py

@@ -55,6 +55,9 @@ class DurationWidget(FormulatorPatch.FloatWidget):
     sub_field_render_list = []
     for title, sub_key, convertion in (('Hour', 'hour', HOUR_IN_SECOND),
                                 ('Minute', 'minute', MINUTE_IN_SECOND)):
+      if value == '':
+        sub_value = ''
+      else:
         sub_value, value = divmod(value, convertion)
       sub_field_render_list.append((title, self.render_sub_field(
                         field, key,