Bug 9432: Plack changes for acqui/addorderiso2409.pl

Without this patch, after selecting the file I want to add acquisitions
from, Plack explodes. With this patch, it works.

To test without Plack:
1) Apply patch.
2) Try adding an order item from a staged file.
3) If it works, there are no regressions from the patch.

To test with Plack:
1) Try adding an order item from a staged file. It will fail.
2) Apply patch.
3) Try adding an order item from a staged file.
3) If it works, the patch is successful.