Create Group overwrites existing groups without warning

Steps to reproduce:
1. Go to Organisation->Groups
2. Add the following group: name = 'aaaa' description 'aaaa'
3. Add the following group: name = 'aaaa' description 'bbbb'

Actual Results:
Adding a new group with the same name as an existing group overwrites the existing group without warning

Expected Results:
The system should notify the user that the group cannot be added because a group with the same name already exists.

Workaround (if any):