Added an .empty() function to the objects, fixes to msgs_ack

The .empty() function returns an "empty" instance of the object
(attributes set to None). This is used rather than using reflection.

The msgs_ack handling broke stuff (InvokeWithLayer when there were
updates), so this is now handled; yet there may be a better fix

telethon/telegram_client.py

@@ -85,6 +85,9 @@ class TelegramClient:
             # We're only interested in the DC options,
             # although many other options are available!
             self.dc_options = result.dc_options
+
+            # We can now enable these (for such methods such as logout)
+            self.sender.ack_requests_confirm = True
             return True
         except RPCError as error:
             print('Could not stabilise initial connection: {}'.format(error))