Error when a command is used

I get the error `(node:2208) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'length' of undefined
    at Client.<anonymous> (/app/test.js:43:61)
    at Client.emit (events.js:196:13)` it's at the `  const commandfile = bot.commands.get(command.slice(prefix));
` part
