Bug 33949: Fix display of old checkouts if no checkouts exist

Bug 33949: Fix display of old checkouts if no checkouts exist

If we pass an empty array from the perl controller, we retrieve an empty
string from the template, and the merge does not work.

This patch fixes the following bug:
Pick a patron without checkout history
Check them an item out and check it in
=> The table is empty, whereas it should display the item that has been
checked in.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>