fix(MessageReactionAdd): prevent double messageReactionAdd triggering (#4682)

Co-authored-by: Sugden <28943913+NotSugden@users.noreply.github.com>
Co-authored-by: SpaceEEC <spaceeec@yahoo.com>

Author: 3 people

src/client/actions/MessageReactionAdd.js

@@ -28,6 +28,8 @@ class MessageReactionAdd extends Action {
 
     // Verify reaction
     if (message.partial && !this.client.options.partials.includes(PartialTypes.REACTION)) return false;
+    const existing = message.reactions.cache.get(data.emoji.id || data.emoji.name);
+    if (existing && existing.users.cache.has(user.id)) return { message, reaction: existing, user };
     const reaction = message.reactions.add({
       emoji: data.emoji,
       count: message.partial ? null : 0,