restricted system commands enabled.
(./lua-parbuilder-weird.tex
warning (parbuilder): found a glue_spec in a paragraph
warning (parbuilder): found a glue_spec in a paragraph
Underfull \hbox (badness 10000) in paragraph at lines 6--6
[]\f x
fine
! error: (parbuilder): weird node 18 in paragraph
! ==> Fatal error occurred, bad output DVI file produced!
No pages of output.