Modified ThinkingSphinx::Search::Query.to_s to handle null conditions and empty conditions

What are your thoughts on this? 

I modified to_s to ignore conditions that are either nil or empty. 

def to_s
    (star_keyword(keywords) + ' ' + conditions.keys.collect { |key|
      "@#{key} #{star_keyword conditions[key], key}" unless ( conditions[key].nil? || conditions[key].empty? )
    }.join(' ')).strip
  end

What is returned in both these cases is similar to a query such as Model.search String.new or Model.search nil.

Thoughts?