config: fix language not saving fixes 1362#

also adds system_lang back to the list it was missing since the switch from dropdown to menu

panels/settings.py

@@ -21,7 +21,6 @@ class Panel(ScreenPanel):
             "type": "menu",
             "menu": "lang"
         }})
-
         self.labels['settings_menu'] = self._gtk.ScrolledWindow()
         self.labels['settings'] = Gtk.Grid()
         self.labels['settings_menu'].add(self.labels['settings'])
@@ -32,7 +31,7 @@ class Panel(ScreenPanel):
         self.labels['lang_menu'] = self._gtk.ScrolledWindow()
         self.labels['lang'] = Gtk.Grid()
         self.labels['lang_menu'].add(self.labels['lang'])
-        for lang in self._config.lang_list:
+        for lang in ["system_lang", *self._config.lang_list]:
             self.langs[lang] = {
                 "name": lang,
                 "type": "button",