Bug 25288: (QA follow-up) Escape data and restore empty list behaviour

Bug 25288: (QA follow-up) Escape data and restore empty list behaviour

After the QA round on bug 25279, some things needed to get fixed:
- Data needs to be escaped
- When no library is defined, we should keep the original behaviour and
  message.
- aria-hidden="true" for FontAwesome coding guideline enforced
- Added role="button" as well.

This patch does that.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>