The code used here has always been "bad" because `about` shouldn't be used
as data source, but the engine probably broke when type checks / dataclasses
for the about parameter in engines has been added with
<https://github.com/searxng/searxng/pull/6258>.
Error log:
```
WARNING searx.engines.public domain im: ErrorContext('searx/engines/public_domain_image_archive.py', 143, '\'url\': _clean_url(f"{about[\'website\']}/images/{result[\'objectID\']}"),', 'TypeError', None, ("'EngineAbout' object is not subscriptable",)) False
ERROR searx.engines.public domain im: exception : 'EngineAbout' object is not subscriptable
Traceback (most recent call last):
File "/home/bnyro/Projects/searxng/searx/search/processors/online.py", line 253, in search
search_results = self._search_basic(query, params)
File "/home/bnyro/Projects/searxng/searx/search/processors/online.py", line 239, in _search_basic
return self.engine.response(response)
~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
File "/home/bnyro/Projects/searxng/searx/engines/public_domain_image_archive.py", line 143, in response
'url': _clean_url(f"{about['website']}/images/{result['objectID']}"),
~~~~~^^^^^^^^^^^
TypeError: 'EngineAbout' object is not subscriptable
```