FIX: If personal messages are disabled, don't show messages for groups

app/assets/javascripts/discourse/controllers/group-activity.js.es6

@@ -6,6 +6,9 @@ export default Ember.Controller.extend({
 
   @computed('model.is_group_user')
   showGroupMessages(isGroupUser) {
+    if (!this.siteSettings.enable_personal_messages) {
+      return false;
+    }
     return isGroupUser || (this.currentUser && this.currentUser.admin);
   }
 });

lib/guardian/group_guardian.rb

@@ -13,6 +13,8 @@ module GroupGuardian
   end
 
   def can_see_group_messages?(group)
-    is_admin? || group.users.include?(user)
+    SiteSetting.enable_private_messages? && (
+      is_admin? || group.users.include?(user)
+    )
   end
 end