fix: make menu entries accessible

assets/controllers/sidebar_menu_controller.js

@@ -12,6 +12,9 @@ export default class extends Controller {
 
     expandedValueChanged(expanded) {
         this.submenuTarget.classList.toggle(this.closedClass, false === expanded)
+        if (false === this.hasButtonTarget) {
+            return
+        }
         this.buttonTarget.setAttribute('aria-expanded', expanded)
         if (false === this.hasIconTarget) {
             return