Update DiscordClient to return a DiscordDmChannel if appropriate
Created by: VelvetThePanda
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Summary
Added a return for DiscordDmChannel instead of DiscordChannel
Details
Build 793 fixed an issue with v8 not sending the channel object in DMs, however various places in the codebase type-check for a DiscordDmChannel, and 793 only provides a DiscordChannel, which causes various checks to fail.
Changes proposed
Return DiscordDmChannel if the guild is null, else return a regular channel
Notes
Any additional notes go here.