query: parsing bug when response in multiple chunks / contains empty row objects

When querying a large bucket like beer-sample and requesting a non-existing attribute in the SELECT clause, server returns a large chunked response (number of documents in bucket) with empty json objects for each document : { }.
Since at least one of the chunks only contains such elements, the parser doesn't find a ":" occurrence and it brings up a bug in section detection : not finding a ":" brings a position of -1, which is always > to the opening bracket position for the parsed row, which triggers a section change attempt.
Then no section header (results, status, signature, errors, etc...) is found and an IllegalStateException is thrown.

Fix the section detection code by checking if nextColon is > -1.