muc.leave_groupchat: could not leave the room

Poezio: 90242b82 + !248 (merged).
Slix: slixmpp@d4067275

On /cycle. Not sure how/why. /close produced the same traceback but closed the tab nonetheless, so I was able to join again afterwards.

2021-08-18 13:33:32,141 DEBUG:multiuserchat:muc.leave_groupchat: could not leave the room sysadmin@joinjabber.org
Traceback (most recent call last):  
  File "/usr/lib/python3.9/site-packages/poezio/multiuserchat.py", line 128, in leave_groupchat
    xmpp.plugin['xep_0045'].leave_muc(jid, own_nick, msg)
  File "/usr/lib/python3.9/site-packages/slixmpp/plugins/xep_0045/muc.py", line 377, in leave_muc
    del self.rooms[room]
KeyError: sysadmin@joinjabber.org