formatter: fix /rss encoding issue
formatter: fix /rss encoding issue

Signed-off-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

inveniosoftware/invenio-formatter,tiborsimko/invenio-formatter,tiborsimko/invenio-formatter,inveniosoftware/invenio-formatter,tiborsimko/invenio-formatter,inveniosoftware/invenio-formatter