
Since the last commit we set the gicon property of StIcon to NULL if an empty string was given when setting the icon name, this means `st_icon_get_icon_name()` will return NULL instead of an empty string. When `getIndicatorIcon()` returns an empty string, the icon_name property will now be set to NULL, so compare it to NULL here. https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/888