don't show XML attributes if they ar eblank or nil

Hi, I'm creating a dynamic xml file using builder in Rails, which pulls from several different related tables. Some of my nodes include attributes, but some don't. I would like to find a way to leave out those attributes that are blank.

My XML now: <row type="bold" line="4"> <cell>Vermont </cell> <cell>27%</cell> </row>

<row type="" line="5"> <cell>Hawaii </cell> <cell>100%</cell> </row>

should look like this: <row type="bold" line="4"> <cell>Vermont </cell> <cell>27%</cell> </row>

<row line="5"> <cell>Hawaii </cell> <cell>100%</cell> </row>

without the blank type="" attribute.

My .builder includes this:

@table.each do |r|       xml.row(:line => r[0], :type=> r[1]) do         r.each do |i|           xml.cell(i, :column_id => '')         end       end     end

I can make the value for :type => nil, but I still get the blank attribute. I tried conditionals inside the node, but that didn't work. Any ideas?

Thanks.