UI Javascript is fragile with respect to HTML formatting

[robx]

(Filing this issue mostly for future reference.)

The UI code relies on rather subtle formatting properties of p.html. Particularly, the use of element.firstChild breaks as soon as whitespace is introduced, e.g. by breaking a line.

Compare https://github.com/robx/pzprjs/pull/122, where autoformatting p.html breaks things.

[JupiLogy]

Maybe related, but the app doesn't load when I'm using the https://darkreader.org/ dynamic filter.