Creating a user from a template with a non-existing group crashes

Description

When a template contains a group which was since deleted, using this template to create a user makes FusionDirectory crash. It should show the error in a pop-up instead.

FusionDirectory Version

1.2

Steps to Reproduce

1. Create a user template with a group
2. Delete the group
3. Create a user from the template

Expected behavior:

An error message and the group is ignored

Actual behavior:

Crash (Fatal Error: Uncaught NonExistingLdapNodeException)