TypeError: 'NoneType' object is not iterable

For me the GoogleImageCrawler of icrawler doesn't work anymore. I updated the user agent in `crawler.py` since that seemed to work in the past, but no luck here. I tried it both on python 3.8 and 3.9 (apple silicon, but shouldn't matter). Again, it worked in the past (like 3-6 months ago).

Even the simple example

```
from icrawler.builtin import GoogleImageCrawler
searchterm = 'ANY SEARCHTERM'
google_crawler = GoogleImageCrawler(storage={'root_dir': 'test'})
google_crawler.crawl(keyword=searchterm, max_num=1)
```

gives
```
...lib/python3.8/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File ".../python3.8/site-packages/icrawler-0.6.6-py3.8.egg/icrawler/parser.py", line 104, in worker_exec
for task in self.parse(response, **kwargs):
TypeError: 'NoneType' object is not iterable
```

Does anyone know how to fix this, or have the same issue in July 2022?