Well, you define less levels than you need.
Try this :
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\definesectionlevels
[default]
[
%chapter, % uncomment this line to make it work
section, subsection, subsubsection, subsubsubsection, subsubsubsubsection]
\starttext
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stoptext
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Interestingly, this will also work, although (if I’m counting correctly) there are still only 5 levels defined, but 6 are used (just like above):
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\definesectionlevels
[default]
[
%chapter, % uncomment this line to make it work
section, subsection, subsubsection, subsubsubsection, subsubsubsubsection]
\starttext
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
%\startsectionlevel
%\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stoptext
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Von: Sylvain Hubert champignoom@gmail.com Gesendet: Dienstag, 28. Mai 2024 10:48 An: mailing list for ConTeXt users ntg-context@ntg.nl Betreff: [NTG-context] lua error in `strc-lev.lua`
ConTeXt LMTX version: 2024.05.27 18:16
Reproducible example:
\definesectionlevels
[default]
[section, subsection, subsubsection, subsubsubsection, subsubsubsubsection]
\starttext
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\startsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stopsectionlevel
\stoptext
lua error > lua error on line 19 in file ./input.tex:
registered function call [969]: ...mtx/tex/texmf-context/tex/context/base/mkiv/strc-lev.lua:75: attempt to index a nil value (field '?') stack traceback: ...mtx/tex/texmf-context/tex/context/base/mkiv/strc-lev.lua:75: in function <...mtx/tex/texmf-context/tex/context/base/mkiv/strc-lev.lua:66> (...tail calls...)