Bug 22735: Resolve internal server error on missing item type

Bug 22735: Resolve internal server error on missing item type

Trivial fix, similar to opac-detail, applied to ISBD and MARC detail.

Test plan:
Enable ArticleRequests pref.
Make sure you have a biblio with no item type in 942c. (Perhaps you need to
make 942c not mandatory temporarily and save a biblio record without this
field being filled.)
If you are logged in, log out.
Go to MARC or ISBD detail page. No crash anymore?

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>