tails-persistence-setup crashes due to missing electrum in feature/buster

electrum was disabled in feature/buster (see #16204 (closed)) which leads to a crash of tails-persistence-setup after the persistence partition has been set up: when the window with the application-related choices is being prepared, the missing electrum icon in the Adwaita theme triggers a crash. Visiting e.g. the /usr/share/icons/Adwaita/scalable/apps directory and copying a random SVG file into electrum.svg prevents the crash.

Affected version: tails-persistence-setup 2.0.2-1.

This was caught by the test suite with persistence.feature (waiting happens for long minutes while the window/app is gone); and reproducing it outside the test suite, starting the application from a terminal, made it possible to figure out what was happening.

Various thoughts:

• This (in lib/Tails/Persistence/Configuration/Setting.pm) should likely try and catch errors, maybe falling back to a “broken image” icon when the requested one isn’t available?

method _build_icon () {
    Gtk3::Image->new_from_pixbuf($self->icon_theme->load_icon(
        $self->icon_name, 48, 'use-builtin'
    ));
}

• Methods mentioned in https://developer.gnome.org/gtk3/stable/GtkImage.html seem to handle the “broken image” part but not those from https://developer.gnome.org/gtk3/stable/GtkIconTheme.html (and we seem to be using those from the latter).

• In the meanwhile, we could patch out the electrum part of the presets through a local patch in tails.git

• Or we could introduce a temporary electrum icon in tails.git; this would solve the crash but I’m not sure what would happen with the other widgets, so I think I’d rather patch out electrum entirely…

Related issues

• Related to #16204 (closed)

Original created by @CyrilBrulebois on 16303 (Redmine)