"Math Processing Error" using CommonHTML with line breaks

Created by: hubgit

An error is thrown when rendering a formula with the CommonHTML renderer in a column that's narrow enough to trigger line breaking, when the linebreaks config is set to automatic: true.

> MathJax.Hub.lastError
> TypeError: Cannot read property 'CHTML' of undefined
    at MML.msubsup.Augment.CHTMLmoveLine (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:521:37)
    at MML.mbase.Augment.CHTMLmoveSlice (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:306:12)
    at MML.mbase.Augment.CHTMLmoveLine (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:267:22)
    at MML.mbase.Augment.CHTMLmoveSlice (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:306:12)
    at MML.mbase.Augment.CHTMLmoveLine (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:267:22)
    at MML.mbase.Augment.CHTMLmoveSlice (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:306:12)
    at MML.mbase.Augment.CHTMLmoveLine (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:267:22)
    at MML.mbase.Augment.CHTMLaddLine (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:195:12)
    at MML.mbase.Augment.CHTMLmultiline (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/autoload/multiline.js?rev=2.6.1:121:12)
    at MML.mrow.Augment.toCommonHTML (https://cdn.mathjax.org/mathjax/2.6-latest/unpacked/jax/output/CommonHTML/jax.js?rev=2.6.1:2593:16)

An example that reproduces the error.

This only occurs when using the CommonHTML renderer - the HTML-CSS renderer doesn't have the same problem.

HTML-CSS:

CommonHTML: