Display of fraction for root index is poor

[NSoiffer]

Issue Summary

The positioning of a fraction when used as the index to \sqrt is pretty bad

Steps to Reproduce:

TeX Input: \sqrt[\frac{1}{2}]{1}

Display:
Normal zoom:

200%:

Other zoom levels also result in poor rendering.

This is likely a result of TeX's rules for positioning the index being suboptimal. I suspect some additions to those rules are needed to avoid having the index crash into the radical.

Technical details:

I viewed this on https://mathjax.github.io/MathJax-demos-web/speech-generator/convert-with-speech.html
Windows machine
The images are from Chrome; theylook similar on Firefox.

[dpvc]

It turns out that this is actually due to incorrectly positioning the surd and bar rather than the position of the 1/2 itself. (Notice that the bottom of the surd isn't low enough.) The CHTML output was correct:

though the position of the fraction isn't great due to the spacing around the fraction from it having TeX class INNER.

I have created a pull request to resolve the issue for the next release.