Null characters are not allowed in deleted message log
Sentry Issue: [BOT-8E](https://sentry.io/organizations/python-discord/issues/1877134544/?referrer=github_integration)

Not sure how a null character even got in there. Does it mean `\\0`?

```
ResponseCodeError: Status: 400 Response: {'deletedmessage_set': [{'content': ['Null characters are not allowed.']}]}
(1 additional frame(s) were not displayed)
...
  File "bot/cogs/moderation/modlog.py", line 577, in on_message_delete
    botlog_url = await self.upload_log(messages=[message], actor_id=message.author.id)
  File "bot/cogs/moderation/modlog.py", line 56, in upload_log
    response = await self.bot.api_client.post(
  File "bot/api.py", line 127, in post
    return await self.request("POST", endpoint, raise_for_status=raise_for_status, **kwargs)
  File "bot/api.py", line 114, in request
    await self.maybe_raise_for_status(resp, raise_for_status)
  File "bot/api.py", line 104, in maybe_raise_for_status
    raise ResponseCodeError(response=response, response_json=response_json)

Unhandled exception in on_message_delete.
```
diff --git a/bot/exts/moderation/modlog.py b/bot/exts/moderation/modlog.py
index 41ed46b6..b01de0ee 100644
--- a/bot/exts/moderation/modlog.py
+++ b/bot/exts/moderation/modlog.py
@@ -63,7 +63,7 @@ class ModLog(Cog, name="ModLog"):
                         'id': message.id,
                         'author': message.author.id,
                         'channel_id': message.channel.id,
-                        'content': message.content,
+                        'content': message.content.replace("\\0", ""),  # Null chars cause 400.
                         'embeds': [embed.to_dict() for embed in message.embeds],
                         'attachments': attachment,
                     }
['bot/exts/moderation/modlog.py']