[v4.beta4] unexpected TeX parser crash (regression from beta3)

[pkra]

The following crashes the TeX parser.

F_{11} \coloneq \mathrm{Hensel\_qf\_unimodular}(F_{11}, p^{-i_1} G_1, p^{-i_1} Z_{11}', a,b)

This appears to be a regression from v4.beta3.

Minimal example: \mathrm{a\_b}.

/node_modules/mathjax-full/mjs/input/tex/TexParser.js:328
                node.childNodes[1].attributes.set(TexConstant.Attr.LATEX, str);
                                   ^

TypeError: Cannot read properties of undefined (reading 'attributes')
    at TexParser.updateResult (/node_modules/mathjax-full/mjs/input/tex/TexParser.js:328:36)
    at TexParser.parse (/node_modules/mathjax-full/mjs/input/tex/TexParser.js:51:14)
    at TexParser.Parse (/node_modules/mathjax-full/mjs/input/tex/TexParser.js:74:18)
    at new TexParser (/node_modules/mathjax-full/mjs/input/tex/TexParser.js:27:14)
    at BaseMethods.MathFont (/node_modules/mathjax-full/mjs/input/tex/base/BaseMethods.js:165:15)
    at CommandMap.parse (/node_modules/mathjax-full/mjs/input/tex/TokenMap.js:108:22)
    at SubHandler.parse (/node_modules/mathjax-full/mjs/input/tex/MapHandler.js:33:32)
    at TexParser.parse (/node_modules/mathjax-full/mjs/input/tex/TexParser.js:50:60)
    at controlSequence (/node_modules/mathjax-full/mjs/input/tex/ParseMethods.js:45:16)
    at RegExpMap.parse (/node_modules/mathjax-full/mjs/input/tex/TokenMap.js:21:49)

Node.js v21.7.1

[pkra]

mathop runs into the same problem, it seems. But \text{} (and plain _) seems to workaround it at least.

[dpvc]

This is a duplicate of #3120 where you reported that earlier. It is the \_, as you have noted, and is fixed in #1028.

[pkra]

Ah, sorry for the noise 😞

[dpvc]

No problem.