Error message when deleting a page that has empty XWikiServerClass object

Steps to reproduce:

1. As Admin (advanced) create a new page
2. Click on Edit Objects
3. Add a XWikiServerClass object (complete required fields)
4. Click Save & View
5. Observe the result
6. Delete the page

Expected results: The page is removed.

Actual results: The page is removed but what appears as an Error message pops on the screen "Some errors happened:•Failed to send event [org.xwiki.bridge.event.DocumentDeletedEvent@d273b126] to listener [org.xwiki.wiki.internal.descriptor.listener.WikiDescriptorListener@1d3bbc]"

Note: No errors in the console and no other information in the UI.