Bug 29282: (follow-up) Account for otherholdings table

Bug 29282: (follow-up) Account for otherholdings table

This patch accounts for the otherholdins table. To test:

1. Turn on SeparateHoldings
2. Find a record where the items are split by SeparateHoldings.
3. Make sure you can hide columns from the table in the Other holdings tab.

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>