overline does not show up for chtml output

Created by: jirilebl

Issue Summary

Using https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml.js (using chrome 91 on linux), "\overline" will just no show up (there is no line).

See https://www.jirka.org/badmj.html

However, moving to https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-svg.js fixes the problem

Steps to Reproduce:

1. Use tex-chtml.js
2. Add (\overline{A})
3. See A without an overline.
4. Switch to tex-svg.js
5. See A with an overline.

Technical details:

• MathJax Version: 3.1.4
• Client OS: Linux PopOS 20.10
• Browser: Chrome 91.0.4472.77

Supporting information:

• Example: https://www.jirka.org/badmj.html
• No errors on the console