The specific error in question is this:
AttributeError: '_MissingSentinel' object has no attribute 'display_avatar'
It throws the error upon trying to set an embed's thumbnail with the following line of code:
embed.set_thumbnail(self.bot.user.display_avatar.url)
However, the error usually goes away when I restart the bot once or twice. I can't observe any pattern with my knowledge. What does this error mean, how can I resolve it, and why does it only sometimes show up? Thank you!