Fixed NLM output test for XSL processors that don't group empty elements.
Fixed NLM output test for XSL processors that don't group empty elements.

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