fallback to 'it_IT.utf8' when locale is not set

src/set-session-language

@@ -35,7 +35,10 @@ class App(tk.Frame):
             )
         self.text.pack(side="top")
         cur_loc = locale.getlocale()
-        self.chosen_locale.set(cur_loc[0]+'.'+cur_loc[1])
+        if cur_loc[0] is None or cur_loc[0] is None:
+            self.chosen_locale.set('it_IT.utf8')
+        else:
+            self.chosen_locale.set(cur_loc[0]+'.'+cur_loc[1])
         self.locale_menu = tk.OptionMenu(self, self.chosen_locale, *self.locales)
         self.locale_menu.pack(side="top")