Test plan:
0) Do not apply the patch
1) Have some overdued checkouts in your database
2) Go to circulation -> overdues (overdues.pl)
3) Try to sort the overdues table by due date and notice it is sorted
alphabetically, not by date
4) Apply the patch
5) Try again and confirm, it is sorted by date
Signed-off-by: Owen Leonard <oleonard@myacpl.org> Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl> Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>