Bug 29026: Restore behavior when an empty barcode field is submitted in circulation

Bug 29026: Restore behavior when an empty barcode field is submitted in circulation

When preference CircAutoPrintQuickSlip is 'clear the screen', when an empty barcode field is submitted in circulation :

Before Bug 17845, behavior was to display empty circulation page (no patron selected).
Now behavior is displaying the circulation page of current patron.

I think previous behavior was used when scanner is used to clear form and wait for another patron card to be scanned.

Test plan :
1) Set system preference CircAutoPrintQuickSlip to 'clear the screen'
2) Go to a patron circulation page
3) Post form without a barcode
=> Check you go to circulation page with no patron selected
4) Set system preference CircAutoPrintQuickSlip to 'open a print quick slip window'
5) Go to a patron circulation page
6) Post form without a barcode
=> Check you go to print quick slip window with correct datas

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>