[6.x] retrieve the model to allow deletion to fire model events

[ivannovak]

Summary

Directly deleting the database entry prevents the deletion model event from firing.

Resolves #382

Explanation

This pull request retrieves the relevant model prior to issuing the deletion so as to trigger the deletion model event.

Checklist

• I've read this template
• I've checked reviewed this PR myself, ensuring consistency and quality with the rest of the project
• I've given a good reason as to why this PR exposes new / removes existing user data