When creating an already existing group, it recreates it over and over again

Steps to reproduce:

1. Go to Administration -> Groups
2. Create a group: 'MyGroup'
3. Create the same group again, with the same name

You'll see that you won't get an alert box with an error (as it should be happening), instead, the page will reload.
Go to the page of your group and check its history.
You'll see that it was recreated.