Comment 6 for bug 1509108

> gtkfilesystemmodel.c:746:gtk_file_system_model_sort: assertion failed: (r == n_visible_rows)
> Aborted (core dumped)

That's an ancient bug in GTK+2 that is supposed to be fixed in GTK+3 only so far:
https://bugzilla.gnome.org/show_bug.cgi?id=697870

It's been taking down arbitrary applications that use GTK+'s internal file dialog, not only Soundconverter.