fix: make subcommand options optional

[gc]

Please describe the changes this PR makes and why it should be merged:

Subcommand options can be optional,
example:

	options: [
		{
			name: 'command',
			description: 'The command you want to invoke.',
			type: ApplicationCommandOptionType.SubcommandGroup,
			options: [
				{
					name: 'spawnrandomcards',
					description: 'Spawn lots of random cards.',
					type: ApplicationCommandOptionType.Subcommand
				}
			]
		}
	],

and discord sends:

[
    {
        "type": 2,
        "options": [
            {
                "type": 1,
                "name": "spawnrandomcards"
                // types think that "options" is always here
            }
        ],
        "name": "command"
    }
]

Reference Discord API Docs PRs or commits:

Not sure if this is even listed in the discord docs, but I deduced this just based off console.log'ing an interaction.