gtk crash on missing icon, packaging problem
To reproduce, see gimp#6165 or 2029, where there is a good technical discussion by GIMP developers.
Symptoms: GTK crashes when icon for "missing" is missing, when a packager such as Ubuntu has failed to install their package "gnome-icon-theme" ( which contains the icon for "missing") as a dependency of their gtk package.
Issue also reported to https://bugs.launchpad.net/ubuntu/+source/gnome-icon-theme/+bug/1881893
It might be a question of fixing it in the right place, or communicating. The GTK project could change their code so it always has a fallback icon to represent a missing icon, reducing dependency? Or the GTK project could change their communication with packagers such as Ubuntu so they understand the dependency? Or Ubuntu packagers could do a better job of reading the GTK communications? Or maybe the bug reporters just don't know who to report it to, maybe to Gnome?
Applies to GTK3 and Ubuntu 20.04