Bug 32631: Error when previewing record during batch record modification

Bug 32631: Error when previewing record during batch record modification

This patch corrects an error in the script which outputs MARC data for
preview during batch record modification.

To test, apply the patch and restart services. You will need at least
one MARC modification template in your system.

- Go to Cataloging -> Batch record modification
- Submit a batch of bibliographic records
- In the table of records that follows, click any "Show MARC" button. A
  modal window should appear with a preview of the modified record.

Signed-off-by: Andrew Fuerste-Henry <andrewfh@dubcolib.org>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>