Bug 14276: Keep highlight on the active item in item editor

Bug 14276: Keep highlight on the active item in item editor

The highlight only works on even items.
This patch should resolve it.

Test plan:
Edit biblio with multiple items.
Verify that the highlight is visible on the selected item you edit.
And that there is no highlight for a new item.

Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>