Some cluster nodes (i.e. logstash nodes or I imagine any with http.enabled set to false) will not have the http_address element as part of their result.  To avoid a NPE need to check that the element exists before trying to get it as a string.
Merge pull request #139 from phospodka/master

bugfix: NPE when discovery is enabled and nodes do not have http_address element
feature: searchResult now provides getters for total & max_score fields - fixes #140