qwebengine_convert_dict Cannot encode command 'TRY ...' to utf8.

qwebengine_convert_dict produces the following error when processing the Kashubian hunspell dictionary with the TRY line. Same for qt5-qtwebengine (change path: bin instead of libexec, and qt5 instead of qt6) and qt6-qtwebengine.

$ /usr/lib64/qt6/libexec/qwebengine_convert_dict /usr/share/hunspell/csb_PL.dic /usr/share/qt6/qtwebengine_dictionaries/csb_PL.bdic
{{[0306/113058.476241:FATAL:aff_reader.cc(327)] Cannot encode command 'TRY ਀䄊...many more characters...਀�' to utf8.}}
Trace/breakpoint trap (core dumped)

$ file /usr/share/hunspell/csb_PL.*
/usr/share/hunspell/csb_PL.aff: Unicode text, UTF-8 text, with very long lines (27428)
/usr/share/hunspell/csb_PL.dic: Unicode text, UTF-8 (with BOM) text

The TRY-line is in /usr/share/hunspell/csb_PL.aff https://src.fedoraproject.org/rpms/hunspell-csb

Other aff files with TRY-line do not produce the error.