gnome-control-center should remove the "mozilla-thunderbird" part from /usr/share/gnome-control-center/default-apps/gnome-default-applications.xml;
alternatively - maybe a cleaner fix - it could follow links before matching the executable.
gnome-control- center should remove the "mozilla- thunderbird" part from /usr/share/ gnome-control- center/ default- apps/gnome- default- applications. xml;
alternatively - maybe a cleaner fix - it could follow links before matching the executable.