The field was missing in Items.pm.
It will still act strangely if you enter a stocknumber that
already exists in the database. (see Bug 5860)
Adding/editing items with stocknumbers you have not used before
should work as expected.
[F. Demians] Was able to reproduce the bug on an UNIMARC DB. The patch works.
Signed-off-by: Frédéric Demians <f.demians@tamil.fr> Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>