Is this something new? Was it working before but some current update has changed behavior? If so you should try 1.0.5 or 1.0.4, and then use git-bisect to narrow down the commit that caused the problem.
As for using the default-config, you are using a ‘blank config’, instead you should use the default-config, you can either just move your configuration out of the way temporally, and it will load the default-config if no other config file is found, or you can find it in $PREFIX/share/fvwm3/default-config/config, and see if that works as well.
Your config is a bit hard to parse (and due to Reads missing bits), but anyways, if you can either track down the commit that cause this to start crashing (if it ever worked) or track down some minimal configuration that causes it to break so it can be tested, then report an issue on github.
Note, the default configuration (if no configuration is found) will read $FVWM_USERDIR/local.config, so if it works in the default config, you can add just the changes to local.config that cause it to crash and share that for testing.
It’s the same with the default config.
Gentoo has only two versions 1.0.4 and live/git, with 1.0.4 there’s no crash so some commit after this release causes this. I’ll check.
I installed VLC here (Debian bullseye), and I don’t get a crash when it finished playing a video or when I closed the app. So might be some issue in VLC in your setup too. Though since some change in fvwm since 1.0.4 is causing the crash, might be a combination of things (makes it harder to debug).
Building from source and using git-bisect until you can narrow down exactly which commit caused the change on your system could help narrow down what in fvwm could have caused the issue, but since I cannot reproduce the issue, I am unable to do the testing.
320ae7aa230106647246d7b19b83a4630956fc93 is the first bad commit
commit 320ae7aa230106647246d7b19b83a4630956fc93
Author: Dominik Vogt <dominik.vogt@gmx.de>
Date: Fri Nov 26 21:41:37 2021 +0100
Fix fvwm missing DestroyNotify events that died before reparenting.
fvwm/add_window.c | 39 ++++++++++++++++++++++++++++++---------
1 file changed, 30 insertions(+), 9 deletions(-)