Hello, I'm trying to convert a urdf model to sdf using the gz sdf tool but it outputs only the following lines:

<sdf version='1.5'>
     <model name='abb_irb14000'/> 
</sdf>

I used the xacro.py tool to get the urdf from a xacro file. Any ideas what could be wrong?

(Here's the urdf file: http://pastebin.com/PgTpGhbp)