During discovery, non-critical error occurs

[emk2203]

During discovery with `pulseaudio-dlna --create-device-config`, I get the following non-critical error:

```bash
Exception in thread Thread-10:
Traceback (most recent call last):
  File "/usr/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.8/threading.py", line 1254, in run
    self.function(*self.args, **self.kwargs)
TypeError: 'ServiceBrowser' object is not callable
```

Program plays music as expected with pulseaudio-dlna.

System is Kubuntu 21.04 (basically identical to 20.10 at the moment). pulseaudio-dlna was installed from the official Ubuntu repo.

Version: pulseaudio-dlna 0.5.3+git20200329-0.1

Bug was reported upstream as well, but is maybe better fixed here.