A bisect with Address Sanitizer enabled indicates this was (silently?)
fixed upstream in commit 908a139753380160563a9d3dbf17fe3d3e4d6fdc,
https://gitlab.com/graphviz/graphviz/-/commit/908a139753380160563a9d3dbf17fe3d3e4d6fdc.
This landed in Graphviz 2.40.0.
