search: facets unicode error fix
search: facets unicode error fix

Signed-off-by: Esteban J. G. Gabancho <03cb568148df368b792a31d9c4d06b12dc802700@gmail.com>

inveniosoftware/invenio-search,inveniosoftware/invenio-search,tiborsimko/invenio-search,tiborsimko/invenio-search