GSocketControlMessage: Don't warn about unknown messages

If we do this, the tests added in bug 673943 will cause warnings.

Signed-off-by: David Zeuthen <davidz@redhat.com>

gio/gsocketcontrolmessage.c

@@ -205,8 +205,15 @@ g_socket_control_message_deserialize (int      level,
 
   g_free (message_types);
 
-  if (message == NULL)
-    g_warning ("unknown control message type %d:%d", level, type);
+  /* It's not a bug if we can't deserialize the control message - for
+   * example, the control message may be be discarded if it is deemed
+   * empty, see e.g.
+   *
+   *  http://git.gnome.org/browse/glib/commit/?id=ec91ed00f14c70cca9749347b8ebc19d72d9885b
+   *
+   * Therefore, it's not appropriate to print a warning about not
+   * being able to deserialize the message.
+   */
 
   return message;
 }