TB on /remove

New traceback due to the sleekxmpp fork update.

<code=python>
File "/home/mathieui/poezio/src/tabs.py", line 1538, in on_input
res = self.input.do_command(key)
File "/home/mathieui/poezio/src/windows.py", line 1219, in do_command
res = Input.do_command(self, key)
File "/home/mathieui/poezio/src/windows.py", line 1039, in do_command
res = self.key_func[key]()
File "/home/mathieui/poezio/src/windows.py", line 1229, in success
res = self.on_success(self.get_text())
File "/home/mathieui/poezio/src/tabs.py", line 1578, in execute_slash_command
self.execute_command(txt)
File "/home/mathieui/poezio/src/tabs.py", line 149, in execute_command
self.commands[command]0
File "/home/mathieui/poezio/src/tabs.py", line 1383, in command_remove
self.core.xmpp.del_roster_item(jid=jid)
File "/home/mathieui/poezio/src/sleekxmpp/clientxmpp.py", line 225, in del_roster_item
return self.client_roster.remove(jid)
File "/home/mathieui/poezio/src/sleekxmpp/roster/single.py", line 188, in remove
return self.update(jid, subscription='remove')
File "/home/mathieui/poezio/src/sleekxmpp/roster/single.py", line 212, in update
self[jid]['groups'] = group
NameError: global name 'group' is not defined