local variable referenced before assignment in poopt

While playing in XMLTab, doing things.

poezio: 7f1e9b08
slixmpp: slixmpp@2a76baf0

2021-09-07 18:53:07,559 ERROR:basexmpp:local variable 'spos' referenced before assignment
Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/slixmpp/xmlstream/xmlstream.py", line 1122, in _safe_cb_run
    cb()
  File "/home/ppjet/Src/poezio/main/poezio/connection.py", line 249, in send_raw
    self.core.handler.outgoing_stanza(data)
  File "/home/ppjet/Src/poezio/main/poezio/core/handlers.py", line 1298, in outgoing_stanza
    self.core.xml_buffer.add_message(
  File "/home/ppjet/Src/poezio/main/poezio/text_buffer.py", line 193, in add_message
    nb = window.build_new_message(
  File "/home/ppjet/Src/poezio/main/poezio/windows/text_win.py", line 93, in build_new_message
    lines = build_lines(
  File "/usr/lib/python3.9/functools.py", line 877, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
  File "/home/ppjet/Src/poezio/main/poezio/ui/render.py", line 117, in build_xmllog
    lines = poopt.cut_text(msg.txt, width - offset - 1)
  File "/home/ppjet/Src/poezio/main/poezio/poopt.py", line 145, in cut_text
    retlist.append((start_pos, spos + 1))
UnboundLocalError: local variable 'spos' referenced before assignment