Bug 7321: Silence some warns in Koha.pm

Bug 7321: Silence some warns in Koha.pm

While testing bug 7013 I noticed a lot of warns in the koha error log.
This patch is silencing them.

To test:
Add or edit an authorised value and check your log files before and after
applying the patch.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
(cherry picked from commit d831a03fdefc56b5462df08cbe626887291c01c8)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>
(cherry picked from commit d3bac2e323a08f31426c768ebd237feb6e4c963b)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>