Error when listening to saving event

Description

Steps to reproduce

1. Create a initializationModule that listens to the Saving event.
2. Go to edit mode and open the developer tool in the browser.
3. Edit a page.
4. You get this an error message.

Expected: Display a warning message like "Publishing or creating event"
Actual: "Unable to load /EPiServer/cms/Stores/contentversion/ status: 409"