Bug 29553: Fix crash on undefined notforloan value

Bug 29553: Fix crash on undefined notforloan value

Test plan:
Set item level itypes to biblioitems.
Find a record with itemtype NULL, having an item.
Place a hold. Without this patch, it crashes.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: ThibaudGLT <thibaud.guillot@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>