Reacting with ❌ doesn't delete generations in DMs

[Kilvoctu]

The bot is able to delete its generations in Discord servers, but not DMs.
It will throw this error

Traceback (most recent call last):
  File "D:\StableDiffusion\aiyabot-git\venv\lib\site-packages\discord\client.py", line 377, in _run_event
    await coro(*args, **kwargs)
  File "D:\StableDiffusion\aiyabot-git\aiya.py", line 74, in on_raw_reaction_add
    message = await self.get_channel(ctx.channel_id).fetch_message(ctx.message_id)
AttributeError: 'NoneType' object has no attribute 'fetch_message'

[Kilvoctu]

Couldn't figure this out, but fortunately there are people way smarter than me.

Used given solution from my own question on stackoverflow. Test to make sure the intended behavior works: bot will delete generated images.

Bug: the bot can delete any of its own messages which contain an embed. This should only affects DMs, and the only other type of message with an embed is /stats, so I'm not too concerned about it at the moment.