[3.20] community/calls: backport crash fix
Taken from https://gitlab.gnome.org/GNOME/calls/-/merge_requests/728
Backport to 3.20 of !66827 (merged).
Taken from https://gitlab.gnome.org/GNOME/calls/-/merge_requests/728
Backport to 3.20 of !66827 (merged).