[Rigo] RigoServiceController: convert app_name=_("Application") to rawstring

If app_name is unicode decoded, the following code will fail (in pl_PL):

  >>> prepare_markup(_("<b>%s</b>, internal error")) % (_("Application"),)

with a nice UnicodeDecodeError due to implicit bytestring decode.
prepare_markup() output is bytestring, _() output is unicode.
Thanks to Enlik for reporting.

rigo/rigo/controllers/daemon.py

@@ -731,7 +731,7 @@ class RigoServiceController(GObject.Object):
         Notify User about Application Management errors.
         """
         if app is None:
-            app_name = _("Application")
+            app_name = prepare_markup(_("Application"))
         else:
             app_name = app.name
         msg = prepare_markup(_("An <b>unknown error</b> occurred"))