title: Discord.js-commando missing argument reply
body: <p>I'm porting my commands from vanilla discord.js to commando framework. I had a command that, when the argument was missing, it warned the user.</p>
  <pre><code>const { Command } = require('discord.js-commando');
  
  module.exports = class ServerCommand extends Command {
      constructor(client) {
          super(client, {
              name: 'say',
              aliases: ['s'],
              group: 'mod',
              memberName: 'say',
              description: 'Make the bot speak for you.',
              userPermissions: ['MANAGE_CHANNELS'],
              examples: [client.commandPrefix + 'say &lt;text&gt;',client.commandPrefix + 'say hello world'],
              args: [{
                  key: 'text',
                  prompt: 'What should the bot say?',
                  type: 'string',
              }]
          })
      }
  
      run(message, { text }) {
          if (text == '' || !text)
              message.say(&quot;You didn't specify what the bot should say.&quot;)
          message.say(text);
          message.delete();
      }
  }
  </code></pre>
  <p>Now, with commando, it automatically warns the user with a reply when the arg is missing.
  My question is, how can I overwrite it?</p>
  <p>Thanks in advance!</p>