Bug 12505 - Acq claim: Show error message when no order is selected

Bug 12505 - Acq claim: Show error message when no order is selected

If no order is selected on the acq claim page when clicking
'Claim order' an ugly perl error message is displayed.

This patch corrects the behaviour to display a human readable
'No order selected'
instead.

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Reworded commit message to reflect what the patch achieves.
Works as described and passes tests.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>