Bug 33047: Return 404 instead of 500 when biblio does not exist

Bug 33047: Return 404 instead of 500 when biblio does not exist

If the biblionumber or the itemnumber passed in parameter does not
exist we should return 404 instead of exploding with a 500.

Test plan:
Attach cover images to biblio and items
Notice that the UI is working correctly (staff and OPAC)
Hit catalogue/image.pl and opac/opac-image.pl with non-existent
biblionumber and imagenumber
Notice that you now get 404 instead of 500

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>