Removal from MUC at server restart caused gajim "programming error" in GLib

Versions

• OS: Linux
• GTK+ Version: 3.24.2
• PyGObject Version: 3.30.4
• python-nbxmpp Version: 0.6.8
• Gajim Version: 1.1.0

Traceback

Traceback (most recent call last):
  File "/usr/lib64/python3.6/site-packages/gi/overrides/GLib.py", line 662, in <lambda>
    func_fdtransform = lambda _, cond, *data: callback(channel, cond, *data)
  File "/usr/lib/python3.6/site-packages/nbxmpp/idlequeue.py", line 563, in _process_events
    return IdleQueue._process_events(self, fd, flags)
  File "/usr/lib/python3.6/site-packages/nbxmpp/idlequeue.py", line 411, in _process_events
    obj.pollin()
  File "/usr/lib/python3.6/site-packages/nbxmpp/transports_nb.py", line 451, in pollin
    self._do_receive()
  File "/usr/lib/python3.6/site-packages/nbxmpp/transports_nb.py", line 676, in _do_receive
    self._on_receive(received)
  File "/usr/lib/python3.6/site-packages/nbxmpp/transports_nb.py", line 690, in _on_receive
    self.on_receive(data)
  File "/usr/lib/python3.6/site-packages/nbxmpp/dispatcher_nb.py", line 537, in _WaitForData
    resp(self._owner, _iq, **args)
  File "/usr/lib/python3.6/site-packages/gajim/common/modules/mam.py", line 465, in _result_finished
    self._mam_query_ids.pop(jid)
KeyError: 'conversations@conference.jabber.de'

Steps to reproduce the problem

No idea. Just happened for the first time. Seems the server shut down and I was removed from the room temporarily: Gajim didn't crash, it just showed the error popup