## Versions:
- OS: Linux 6.1.1-1-default
- GTK Version: 3.24.35
- PyGObject Version: 3.42.2
- GLib Version : 2.74.0
- python-nbxmpp Version: 3.2.5
- Gajim Version: 1.5.4

## Traceback
```
Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/nbxmpp/task.py", line 306, in
_on_timeout
    self._set_finished()
  File "/usr/lib/python3.10/site-packages/nbxmpp/task.py", line 242, in
_set_finished
    self._finalize()
  File "/usr/lib/python3.10/site-packages/nbxmpp/task.py", line 368, in
_finalize
    self._client._dispatcher.remove_iq_callback(self._iq_id)
AttributeError: 'NoneType' object has no attribute 'remove_iq_callback'

```
## Steps to reproduce the problem
start the program and connect for a while, program will crash