Handle case when action id does not have number at end

assets/javascripts/discourse/components/wizard-links.js.es6

@@ -79,7 +79,8 @@ export default Component.extend({
       if (items.length) {
         next = Math.max.apply(Math, items.map((i) => {
           let parts = i.id.split('_');
-          return parts[parts.length - 1];
+          let lastPart = parts[parts.length - 1];
+          return isNaN(lastPart) ? 0 : lastPart;
         })) + 1;
       }