Unable to set any other language (`! Argument of \str_uppercase:n has an extra }.`)

[Asmilex]

Hello! It seems that setting lang to values such as "de" or "es" are not working.

pandoc.exe --from markdown --template eisvogel.tex --listings --top-level-division="chapter" --pdf-engine=xelatex -o TFG.pdf ./chapters/00-dedication.md ./chapters/01-overview.md ./chapters/02-lorem_ipsum.md 00-meta.md
Error producing PDF.
! Argument of \str_uppercase:n has an extra }.
<inserted text>
                \par
l.136   \setmainlanguage[]{}

It was also mentioned in #240. Could it be related to this bug in pandoc?

I'm using pandoc version 2.17.0.1 and the lastest Eisvogel release.

[humbinal]

I also ran into the same problem, it turned out that this may be a bug in pandoc, and I need everyone's help urgently！

[Nainterceptor]

Same issue here, but don't know how to help 🤷‍♂️