#line_number_from should return nil since we don't support line numbe…

…rs right now

See: sparklemotion/nokogiri#1223

lib/rosette/extractors/xml-extractor.rb

@@ -112,7 +112,10 @@ def name_from(node)
         end
 
         def line_number_from(node)
-          node.line
+          # Nokogiri supports `node.line`, but it doesn't return
+          # correct line numbers when running on JRuby. See:
+          # https://github.com/sparklemotion/nokogiri/issues/1223
+          nil
         end
 
         def unescape(text)