Bug 22058: Fix display of empty table cells in OPAC MARC view holdings

Bug 22058: Fix display of empty table cells in OPAC MARC view holdings

I compared the template logic to the MARC detail page in staff.
We use $raw there instead of html, which will also make notes and other
fields with HTML in them display correctly. I am proposing to use the
$raw filter in OPAC as well.

To test:
- Go to the OPAC
- Search for a record with items
- Switch to the MARC view
- Verify empty cells show   (html entity for space)
- Apply patch
- Repeat test
- Verify empty table cells now show as empty

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>