Bug 23363: Fix Internal Server Error when clicking on shipment cost invoice link

Bug 23363: Fix Internal Server Error when clicking on shipment cost invoice link

To test:

On the fund detail page, have some shipment costs associated with a fund

an example would be cgi-bin/koha/acqui/spent.pl?fund=<your fund>&fund_code=<your
code>

Click the link for the fund, without this patch it will give an internal
server error.

With this patch, the shipment invoice will be loaded.
Signed-off-by: Jason DeShaw <JDeShaw@fargolibrary.org>
Signed-off-by: Laurel Moran <lmoran@sdlawlibrary.org>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>