Markdown in a model error

[samuelcolvin]

Markdown in a model gives this error

react-dom.production.min.js:189 Error: Minified React error #426; visit https://reactjs.org/docs/error-decoder.html?invariant=426 for the full message or use the non-minified dev environment for full errors and additional helpful warnings.
    at pm (react-dom.production.min.js:278:279)
    at Qi (react-dom.production.min.js:280:200)
    at Ea (react-dom.production.min.js:271:88)
    at yf (react-dom.production.min.js:273:300)
    at yn (react-dom.production.min.js:127:105)
    at react-dom.production.min.js:267:273
fa @ react-dom.production.min.js:189
Xp.n.callback @ react-dom.production.min.js:189
qc @ react-dom.production.min.js:144
hf @ react-dom.production.min.js:262
fm @ react-dom.production.min.js:260
Ny @ react-dom.production.min.js:259
Ly @ react-dom.production.min.js:283
En @ react-dom.production.min.js:281
yf @ react-dom.production.min.js:273
yn @ react-dom.production.min.js:127
(anonymous) @ react-dom.production.min.js:267
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react-dom.production.min.js:278 Uncaught Error: Minified React error #426; visit https://reactjs.org/docs/error-decoder.html?invariant=426 for the full message or use the non-minified dev environment for full errors and additional helpful warnings.
    at pm (react-dom.production.min.js:278:279)
    at Qi (react-dom.production.min.js:280:200)
    at Ea (react-dom.production.min.js:271:88)
    at yf (react-dom.production.min.js:273:300)
    at yn (react-dom.production.min.js:127:105)
    at react-dom.production.min.js:267:273