Problem with undefined chunks

[SnarkBoojum]

I have a problem trying to get bublé in Debian : for some reason, it manages to trigger a code path where chunk ends up undefined, so I get an error. With the attached patch, I get my tentative bublé to accept the sample code given on the bublé homepage (which still points to gitlab although the last version is only on github...)

fix_undefined_chunk.txt