Bug 34694: Only check for IsAvailableForItemLevelRequest if is authenticated

Bug 34694: Only check for IsAvailableForItemLevelRequest if is authenticated

- Go to circulation rules and set On shelf holds allowed to If all unavailable
- Log out
- Visit a bib record on OPAC:
http://localhost:8080/cgi-bin/koha/opac-detail.pl?biblionumber=76
- Notice it blows up with error 500
- Apply patch. Repeat

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 1742913a0522c589705c5e54ce13c6ef1c7463ea)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>