fix KeyError in group_edit

ldap_frontend/__init__.py

@@ -217,7 +217,7 @@ def group_edit(ldap, ou):
             )
             flash(
                 gettext(
-                    "%(user)s was added to %(ou)s", user=request.form["remove"], ou=ou
+                    "%(user)s was added to %(ou)s", user=request.form["add"], ou=ou
                 )
             )