Repeatedly sending customer notifications on requests with invalid request types

Summary

Some users are receiving repeatedly notifications for resolved requests with changed issue types.

Environment

Cloud + Classic project

Steps to Reproduce

1. Go to Project Settings -> Customer Notifications;
2. Edit the customer notification for Request Resolved;
3. In the content of the Request Resolved notification, add the field ${request.status} and save;
4. In Project Settings -> Language support;
5. Create a new translation for the same notification but without the ${request.status} variable;
6. Raise a request;
7. As an agent, change the issue type of the request (this will leave the issue with an invalid Request type), see attached image (screenshot-1) for what this looks like in old issue view;
8. Add 2 customers as participants, each one with a different language that the notification has translations for;
9. Trigger the customer notification by resolving the issue.

Expected Results

Both customers should receive just 1 notification when the request is resolved.

Actual Results

The customer using the language without the customised translation with ${request.status} will receive 21 notifications regarding the resolved request.

Workaround

To temporarily solve the problem, remove any ${request.status} field out of the content of any customer notification for Request Resolved.