Resolving the crashes found through fuzz testing by HongxuChen.

This is the patch contained in a mail to debian-devel: https://lists.debian.org/debian-devel/2022/08/msg00035.html slightly modified (with dgit) to fit in with existing debian/patches

I've also enabled (in previous commits) salsa-ci/pipeline, which at least shows that this patch does not cause a regression regarding building/autopkgtests/lintian...

Beyond that, I'm afraid I cannot vouch for this (although it does look reasonable to my rather rusty C) -- Philip Hands