Set value before validate record in button click

issue3322
review1022002
(transplanted from 93fe795cf2b97437598e9155a77957c48e0a1ae0)

tryton/gui/window/view_form/view/form.py

@@ -178,6 +178,7 @@ class ViewForm(ParserView):
 
     def button_clicked(self, widget):
         record = self.screen.current_record
+        self.set_value()
         fields = self.get_fields()
         if not record.validate(fields):
             self.screen.display()