Fix missing flag xfce4-xkb-plugin

When I use this plugin to change the keyboard layout to arabic. Text "ara" is appear instead of arabic flag.

I see arabic flag in /usr/share/xfce4/xkb/flags/ which has name sa.svg. To display flag in panel, simply copy or make link to ara.svg from that file.
$ cd /usr/share/xfce4/xkb/flags/
$ sudo ln -s sa.svg ara.svg