Bug 12264: [QA Follow-up] Fixing biblionumber/biblioitemnumber mixup

Bug 12264: [QA Follow-up] Fixing biblionumber/biblioitemnumber mixup

While testing the string change on 12264, I had this result:
DBD::mysql::st execute failed: Column 'biblioitemnumber' cannot be null at /usr/share/koha/testclone/C4/Items.pm line 2191.
DBD::mysql::st execute failed: Column 'biblioitemnumber' cannot be null at /usr/share/koha/testclone/C4/Items.pm line 2191.
    # Child (GetItemsInfo tests) exited without calling finalize()
not ok 4 - GetItemsInfo tests

This was caused by this line in the unit test:
 my $biblionumber = get_biblio();
This routine returns:
    return ($bibnum, $bibitemnum);
So instead of the bibnum the bibitemnum is saved in biblionumber.
In my test database bibnum and bibitemnum somehow got out of sync, revealing
this bug :)
The fix is just adding parentheses:
 my ( $biblionumber ) = get_biblio();

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>