Bug 26102: Prevent XSS when To.json is used: unimarc_field_4XX.tt

Bug 26102: Prevent XSS when To.json is used: unimarc_field_4XX.tt

To test, edit a MARC framework to link a subfield to the
unimarc_field_4XX.tt. The process of triggering the plugin and selecting
a search result from the plugin popup should work correctly.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit dbd13593538b8dbba9dfe9ff200b1d472ec0595b)
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>