Debian has dash as default shell.
It isn't done automatically by nm-applet itself since nm-applet 0.9.9.0 (fc19+), this one commit: https://git.gnome.org/browse/network-manager-applet/commit?id=276a702000ee9e509321891f5ffa9789acfb053c At the same time they've introduced option to manually hide the icon: https://git.gnome.org/browse/network-manager-applet/commit?id=e7331a3f33ab422ea6c1bbc015ad44d8d9c83bc3