"action_deactivate_form" is only making required slot null. But not all form slots

Version: Rasa X 0.31.0

Check the story

## just stop, signup, don't continue
* signup
    - signup_form
    - form{"name": "signup_form"}
* stop
	- utter_ask_continue_signup
* deny
    - utter_thumbsup
	- action_deactivate_form
    - form{"name": "null"}`

On denying the form. The form is getting deactivated but it not emptying all of the slots except the requested_slot