Bug 33578: Fix controller when editing a restriction type

Bug 33578: Fix controller when editing a restriction type

Do not display a warning when we are editing a restriction type and no
other types with this description exists.

Signed-off-by: Michaela Sieber <michaela.sieber@kit.edu>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit b5de15c4b8daccfb80718e82633553f7dbb8b623)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 61b9002848cdb316da6405f615bb4ca746dab26a)
Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>