bug#56651: Gajim 1.4.6: Error on logging into account

[Joseph Turner]

## Versions:
- OS: Linux 5.10.0-14-amd64
- GTK Version: 3.24.30
- PyGObject Version: 3.40.1
- GLib Version : 2.70.2
- python-nbxmpp Version: 3.1.0
- Gajim Version: 1.4.6

## Traceback
```
Traceback (most recent call last):
  File 
"/gnu/store/s6s4lrjwa5yxv5cz0sc1s38vy2jsnxni-gajim-1.4.6/lib/python3.9/site-packages/gajim/gtk/controls/groupchat.py",
 line 285, in update_actions
    joined = self.contact.is_joined
AttributeError: 'BareContact' object has no attribute 'is_joined'

```
## Steps to reproduce the problem
1. Open gajim.
2. Enter correct password.

I am running Guix on a foreign distro (Debian bullseye).
...