Bot sends no send messages in this channel permission DM for invalid commands

[Sqaaakoi]

To reproduce:

• Send any message starting with the / or ./ (or any other supported prefix) in a channel the bot doesn't have permission to send messages in
• Recieve I don't have permission to write in this channel.

[brtwrst]

Thanks for reporting. Fixed by https://github.com/engineer-man/piston-bot/commit/04305f142abbff0733fec02844773158c153c2be