Clear modified fields when cancelling record

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

@@ -229,6 +229,7 @@ class Record(SignalEvent):
 
     def cancel(self):
         self._loaded.clear()
+        self.modified_fields.clear()
 
     def get_timestamp(self):
         result = {self.model_name + ',' + str(self.id): self._timestamp}