Blocked self-message makes poezio respond with error.

Situation:

1. install mod_firewall that rejects certain messages
2. Send a messages that gets rejected from poezio to another client (resource locked)
3. Poezio will get an error message
4. Poezio will respond to the error message with an error message.

poezio log:

2017-03-29 18:44:40,742 DEBUG:xmlstream:SEND: <message to="georg@yax.im/other" id="ceac8d32-9fce-48c4-b7b6-1f2c7fac3036-15AF" xml:lang="en" type="chat">evil content</message>
[snip]
2017-03-29 18:44:40,831 DEBUG:xmlstream:RECV: <message id="ceac8d32-9fce-48c4-b7b6-1f2c7fac3036-15AF" type="error" from="georg@yax.im/other" to="georg@yax.im/poezio"><error type="cancel"><not-allowed xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" /><text xmlns="urn:ietf:params:xml:ns:xmpp-stanzas">Blocked due to abuse</text></error></message>
2017-03-29 18:44:40,840 DEBUG:xmlstream:Event triggered: message_error
2017-03-29 18:44:40,846 DEBUG:xmlstream:SEND: <message id="ceac8d32-9fce-48c4-b7b6-1f2c7fac3036-15AF" type="error" to="georg@yax.im/other"><error type="cancel"><undefined-condition xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" /><text xmlns="urn:ietf:params:xml:ns:xmpp-stanzas">Slixmpp got into trouble.</text></error></message>
2017-03-29 18:44:40,849 ERROR:rootstanza:Error handling {jabber:client}message stanza
Traceback (most recent call last):
  File "/usr/src/poezio/poezio-venv/src/slixmpp/slixmpp/xmlstream/xmlstream.py", line 753, in event
    handler_callback(data)
  File "/usr/src/poezio/poezio/core/handlers.py", line 240, in on_error_message
    if not tab.nack_message('\n' + error, message['id'], message['to']):
  File "/usr/src/poezio/poezio/tabs/basetabs.py", line 775, in nack_message
    new_msg = self._text_buffer.nack_message(error, msg_id, msg_jid)
  File "/usr/src/poezio/poezio/text_buffer.py", line 166, in nack_message
    return self._edit_ack(-1, old_id, jid, append=error)
  File "/usr/src/poezio/poezio/text_buffer.py", line 179, in _edit_ack
    (old_id, msg.jid, jid))
poezio.text_buffer.AckError: Wrong JID for message id ceac8d32-9fce-48c4-b7b6-1f2c7fac3036-15AF (was None, expected georg@yax.im/poezio)
2017-03-29 18:44:40,851 ERROR:basexmpp:Wrong JID for message id ceac8d32-9fce-48c4-b7b6-1f2c7fac3036-15AF (was None, expected georg@yax.im/poezio)
[snipped duplicate traceback]