% lilypond-book --safe --output out safe-mode-crash.lytex
\documentclass{article}
\begin{document}

\begin{lilypond}
\markup{
\fret-diagram-terse #"x;3;2;o;1;o;"
}
\end{lilypond}
%
\begin{lilypond}
\markup{
\fret-diagram-terse #"x;x;o;2;3;2;"
}
\end{lilypond}

\end{document}