Bug 26627: Print and confirming a hold can cause an infinite loop

Bug 26627: Print and confirming a hold can cause an infinite loop

Test plan:
1) Place a hold for pickup at library A
2) Confirm the hold and print slip
3) Checkin the item again
4) Confirm the hold and print slip
5) The modal returns, do it again
6) Apply this patch
7) Reload the page
8) Repeat steps 1-3
9) No loop!

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>