Resolve telethon issues

[loganwilliams]

• [x] Selenium driver not working for screenshots (however this fix uses a FirefoxProfile which has apparently been deprecated, so it would be nice to find a non-deprecated way to do this)
• [x] Message comparison weirdness, int vs str (fixed by adding another len, but not sure if this is the intended logic
• [x] Garbled Cyrillic text in HTML output -- possibly a character encoding issue when something is upload to S3
• [x] post can be None? This throws the error quoted below:

2022-03-18 11:06:22.340 | ERROR    | __main__:process_sheet:134 - Got unexpected error in row 2879 with archiver TelethonArchiver for url [...]: 'NoneType' object has no attribute 'grouped_id'
Traceback (most recent call last):
  File "/Volumes/Oxygen/auto-archiver/auto_archive.py", line 131, in process_sheet
    result = archiver.download(url, check_if_exists=True)
  File "/Volumes/Oxygen/auto-archiver/archivers/telethon_archiver.py", line 65, in download
    media_posts = self._get_media_posts_in_group(chat, post)
  File "/Volumes/Oxygen/auto-archiver/archivers/telethon_archiver.py", line 41, in _get_media_posts_in_group
    if post.grouped_id == original_post.grouped_id and post.media is not None:
AttributeError: 'NoneType' object has no attribute 'grouped_id'

[msramalho]

approved so far, can look at other issues afterwards

[msramalho]

Fixed all issues reported.