documentclass{scrartcl}
usepackage{fontspec}

begin{document}
Hallo
end{document}

xelatex -synctex=1 -interaction=nonstopmode -shell-escape %.tex

! LaTeX error: "kernel/invalid-variant"
! Variant form 'e' invalid for base form 'tl_if_empty_p:n'.
! See the LaTeX3 documentation for further information.