Bug 7485 - Cannot edit barcode on Fast Add

Bug 7485 - Cannot edit barcode on Fast Add

Simple fix, a special case was added for the fast add framework
in the case that an item was being checked out that had not been
catalogued. In that case, the barcode was being passed as a parameter
through addbiblio.pl to additem.pl.

This barcode param was used to overwrite the existing value, so if
no barcode param was passed ( which is only the case with fast adds
from the circ screen ), the barcode field would appear empty in the
items editor.

This commit causes that special case code to check for an existing
barcode value first, and only use the cgi parameter 'branch' in the
case that there is no existing barcode value.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Editing barcode of fast added item now works. Passes t xt

Recommend this for 3.6 release.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>