Events that have an anonymous enrollment are visible for non-logged-in users, even if their visibility is changed to "community" or "group"

Problem/Motivation

Events that have an anonymous enrollment are visible for non-logged-in users, even if their visibility is changed to "community" or "group".

This is clearly a bug, and could lead to events unintentionally visible for anonymous users.

Steps to reproduce

1) Create an event in a group, set visibility to public and enable anonymous enrollment
2) Enrol to this event while not logged in, creating an anonymous enrollment
3) Change the visibility of the event to "group"
4) Try to access the event while not logged in -> it is still accessible
5) Delete the enrollment you just created
6) Try to access the event while not logged in -> it is no longer accessible

Expected behaviour

Changing the accessibility of an event away from "Public" should immediately make it non-public, even if anonymous enrollments exist.