Bug 20422: Add unit test to Output.t for parametrized_url

Bug 20422: Add unit test to Output.t for parametrized_url

This test will reveal that we need to resolve a warning too.

Test plan:
[1] Run t/Output.t without the second patch.
[2] The test will fail on the warning raised by an undefined value.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>