Bug 28103: Fix barcode plugin on the order receive view

Bug 28103: Fix barcode plugin on the order receive view

Fix the following error:
Uncaught TypeError: Cannot read property 'field_value' of null

Test plan:
Set "AcqCreateItem" to "receiving an order"
Set "autoBarcode" to "generated in the form <branchcode>yymm0001"

Create an order and go to receive it at a path like
/cgi-bin/koha/acqui/orderreceive.pl?ordernumber=2&invoiceid=1

Click on the barcode input and confirm that it's prefilled
automatically

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>