fix(Webhook): throw an error if no token is available when it's required (#5798)

src/errors/Messages.js

@@ -92,6 +92,7 @@ const Messages = {
   INVALID_ELEMENT: (type, name, elem) => `Supplied ${type} ${name} includes an invalid element: ${elem}`,
 
   WEBHOOK_MESSAGE: 'The message was not sent by a webhook.',
+  WEBHOOK_TOKEN_UNAVAILABLE: 'This action requires a webhook token, but none is available.',
   MESSAGE_REFERENCE_MISSING: 'The message does not reference another message',
 
   EMOJI_TYPE: 'Emoji must be a string or GuildEmoji/ReactionEmoji',