fix register

vispa/controller/ajax.py

@@ -48,8 +48,9 @@ class AjaxController(AbstractController):
         session = cherrypy.request.db
 
         user_group = vispa.config("usermanagement", "user_group", "user")
-        user_group = Group.get_by_name(session, user_group)
-        user_group.add_user(session, user, Group_User_Assoc.CONFIRMED)
+        if user_group:
+            user_group = Group.get_or_create_by_name(session, user_group)
+            user_group.add_user(session, user, Group_User_Assoc.CONFIRMED)
 
         if vispa.config("web", "registration.autoactive", True):
             return { "hash": user.hash }