Restore invitation code logic

client/components/settings/invitationCode.js

@@ -1,6 +1,6 @@
 Template.invitationCode.onRendered(() => {
   const setting = Settings.findOne();
-  if (setting || setting.disableRegistration) {
+  if (!setting || !setting.disableRegistration) {
     $('#invitationcode').hide();
   }
 });