ctop.xsl missing parens for minus?

[GoogleCodeExporter]

What steps will reproduce the problem?
Transform the following content markup:

<math xmlns='http://www.w3.org/1998/Math/MathML'>
<apply>
  <minus/>
  <cn>1</cn>
  <apply>
    <minus/>
    <cn>9</cn>
    <cn>2</cn>
  </apply>
</apply>
</math>

using ctop.xsl

What is the expected output? What do you see instead?
I would have expected to see 1 - (9-2).
Instead I see 1 - 9 - 2. The underlying XML does not contain mo's for parens, 
or mfenced.

What version of the product are you using? On what operating system?
Testing using the latest version of ctop.xsl from this website as of 9/20/11, 
on Ubuntu 11.04, Firefox 6.02.

Please provide any additional information below.
I'm new to MathML in general, and so may be providing bad input, or doing 
something else incorrectly, but I'm seeing lots of other correctly rendered 
transformations, just not things involving precedence and the minus operator. 

Original issue reported on code.google.com by [email protected] on 20 Sep 2011 at 3:11