feat: throw custom error for uncached Guild#me (#3271)

* handle cases where Guild#me is uncached

* fix id prop

* remove unnecessary checks

* space's requested changes

src/errors/Messages.js

@@ -79,6 +79,7 @@ const Messages = {
   GUILD_CHANNEL_ORPHAN: 'Could not find a parent to this guild channel.',
   GUILD_OWNED: 'Guild is owned by the client.',
   GUILD_MEMBERS_TIMEOUT: 'Members didn\'t arrive in time.',
+  GUILD_UNCACHED_ME: 'The client user as a member of this guild is uncached.',
 
   INVALID_TYPE: (name, expected, an = false) => `Supplied ${name} is not a${an ? 'n' : ''} ${expected}.`,