As a continued fix for http://bugzilla.ecoinformatics.org/show_bug.cgi?id=2469,
I've fixed the indexing implementation in both buildIndex() and
traverseParents(). Duane pointed out that the incorrect parent node ids
were being indexed in xml_path_index, causing some stylesheets to render
metadata incorrectly. I've changed buildindex() to index the correct parent id,
and have changed traverseParents() to only index paths that actually contain
node data (some TEXT nodes exist with empty data).