Invalid group names can be introduced when creating a new entry.

[CostiChD]

Steps to reproduce:

1. Go to Flash Messages homepage
2. Click on the "Create" button to create a new entry
3. Select the Flash Messages template
4. Click on the "Create" button
5. In edit mode, in the "GROUPS" label write a random value.
6. Click on the "Save and View" button

Note1: Going in view mode and clicking on the group name(the random value) sends the user to a nonexistent page.

Note2: The solution could be a picker for groups.

[CostiChD]

Closing this since it was fixed (#11), but not yet released.