[s3] query should default to empty hash

lib/fog/aws/s3.rb

@@ -209,7 +209,7 @@ DATA
           end
           canonical_resource << "#{params[:path]}"
           canonical_resource << '?'
-          for key in params[:query].keys
+          for key in (params[:query] || {}).keys
             if ['acl', 'location', 'logging', 'requestPayment', 'torrent', 'versions', 'versioning'].include?(key)
               canonical_resource << "#{key}&"
             end