Fix the groups on events UX
There's a bug (see below) with the groups field, related to permissions.
Better solution is to fix this whole sorry mess, and make a better UX.
Suggestion remove the groups from the edit form. Default to the existing groups (or for a new node the groups it is being posted to). Add another form to add additional groups that is separate. This will be the path of least resistance in D8 when we get there too.