DefaultUrlHelper.buildParametersString appends just ? if collection is empty

DefaultUrlHelper.buildParametersString() checks that it has parameters to append before adding the first "?"/"&", but if the only parameters are empty Iterables/Arrays, then it shouldn't do that.

I'd suggest adding the new query string to a StringBuilder, and then if it is non-empty, append that with the separator to the link at the end. (See patch)