Custom slot mapping is producing None value

Rasa Open Source
2

In my submit() I logged the destination slot correctly. So I got a workaround where I get the slot value from the tracker and pass it as a renamed variable to the utter template.

def submit(
        self,
        dispatcher: CollectingDispatcher,
        tracker: Tracker,
        domain: Dict[Text, Any],
    ) -> List[Dict]:
        logging.info(tracker.get_slot('destination'))
        dispatcher.utter_message(
            template="utter_show_directions", destination_value=tracker.get_slot('destination'))
        return []

So utter_show_directions uses {destination_value} now.

I still think this is a bug and the first approach should work, right?