Bug 36858: Check page parameter for virtual shelves

Bug 36858: Check page parameter for virtual shelves

Test plan:
Try passing page=x now and verify different behavior (no 500).

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 90f011355735d16af8cdf6ef224ccf8074ad94e1)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit d903ffd4e61689ddcac0f4cd046d2b9f800859f3)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>