Error handling for commands / Handling edge cases

[matta174]

Basically if a game wasn't found or if there are no expansions etc we want the bot to respond with that information rather than just not responding

[joshua-nicholson]

According to this we should only add error messages if the user uses a command improperly but should fail silently if they enter a command that doesn't exist

https://github.com/meew0/discord-bot-best-practices