Bug with invalid mathml

[Klortho]

This works fine:

http://localhost:16000/?q=y2

This correctly produces an error message about invalid mathml:

http://localhost:16000/?q=y2</math

But this just produces a blank screen, which is bad:

http://localhost:16000/?q=<mfracy2

This seems to be a problem with MathJax inside PhantomJS. For some reason, the MathJax error is not getting communicated back out. Try this:

• Load up the engine.html page in a browser (make sure it's being served by a web server)
• Change, temporarily, the mathjax script url to http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_SVG.

Then enter this in the console:

engine.process({ 'in_format': 'mml',
        q:'<math><mfrac<mi>y</mi><mn>4</mn></mfrac></math>'
      }, 
      function() { console.log("done"); }
);

You should see the mathjax error message where the second formula was.