Bug 35149: Add Option to ignore submit of checkout field when empty

Bug 35149: Add Option to ignore submit of checkout field when empty

1) Apply patch
2) Set CircAutoPrintQuickSlip to "do nothing"
3) Go to the checkouts form for a specific patron
4) Submit the form with empty value
5) Verify that no action is taken and you stay on the current page

Signed-off-by: Laura Escamilla <laura.escamilla@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 3d030ded6bc3d60b6a6e0ca8c6c648b5bb167e0e)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>