deezerart: fixed crash if artist similarity is below threshold

[phw]

If the artist similarity is below the configured threshold the plugin crashed with:

Traceback (most recent call last):
  File "/tmp/.mount_MusicBdwLOgu/usr/conda/lib/python3.12/site-packages/picard/webservice/__init__.py", line 593, in _process_reply
    self._handle_reply(reply, request)
  File "/tmp/.mount_MusicBdwLOgu/usr/conda/lib/python3.12/site-packages/picard/webservice/__init__.py", line 581, in _handle_reply
    handler(bytes(reply.readAll()), reply, error)
  File "/home/phw/Applications/MusicBrainz-Picard-daily-x86_64.AppImage.config/MusicBrainz/Picard/plugins/deezerart/deezer/client.py", line 57, in handler
    callback(result, error)
  File "/home/phw/Applications/MusicBrainz-Picard-daily-x86_64.AppImage.config/MusicBrainz/Picard/plugins/deezerart/__init__.py", line 133, in _queue_from_search
    self.log_debug('artist similarity below threshold: %r ~ %r', artist, result.artist.title)
                                                                         ^^^^^^^^^^^^^^^^^^^
AttributeError: 'Artist' object has no attribute 'title'
Aborted (core dumped)