Bug 9503 Correct name of parameter passed to parcel.pl

Bug 9503 Correct name of parameter passed to parcel.pl

invoiceid was being passed as invoice causing GetInvoiceDetails
to silently fail and a system error downstream when
accessing the 'orders' element of the undefined invoice

Added an error message if GetInvoiceDetails called on undef

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>