fix(GuildEmoji): added a check for managed emojis in fetchAuthor (#2645)

src/errors/Messages.js

@@ -94,6 +94,7 @@ const Messages = {
   WEBHOOK_MESSAGE: 'The message was not sent by a webhook.',
 
   EMOJI_TYPE: 'Emoji must be a string or GuildEmoji/ReactionEmoji',
+  EMOJI_MANAGED: 'Emoji is managed and has no Author.',
 
   REACTION_RESOLVE_USER: 'Couldn\'t resolve the user ID to remove from the reaction.',
 };

src/structures/GuildEmoji.js

@@ -1,5 +1,6 @@
 const GuildEmojiRoleStore = require('../stores/GuildEmojiRoleStore');
 const Permissions = require('../util/Permissions');
+const { Error } = require('../errors');
 const Snowflake = require('../util/Snowflake');
 const Emoji = require('./Emoji');
 
@@ -87,6 +88,9 @@ class GuildEmoji extends Emoji {
    * @returns {Promise<User>}
    */
   fetchAuthor() {
+    if (this.managed) {
+      return Promise.reject(new Error('EMOJI_MANAGED'));
+    }
     return this.client.api.guilds(this.guild.id).emojis(this.id).get()
       .then(emoji => this.client.users.add(emoji.user));
   }