Bug 25869: Fix Coce display for lists

Bug 25869: Fix Coce display for lists

To test:
1 - Enable Coce for Opac
    CoceHost: https://coce.bywatersolutions.com
    CoceProviders: Select all
    OpacCoce: Enable
2 - Do a search on the Opac, confirm you see some covers
3 - Add some of the items with covers to a public list
4 - View the public list
5 - Note no covers display
6 - Apply patch
7 - Success!

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>