fix: make nav controller more universal

public/typo3conf/ext/ep_theme/Resources/Private/Assets/js/controllers/nav_controller.js

@@ -21,12 +21,16 @@ export default class extends Controller {
     }
 
     expandedValueChanged(expanded) {
-        this.buttonTarget.setAttribute('aria-expanded', expanded)
-        this.subnavTarget.setAttribute('aria-hidden', !expanded)
-        if (true === expanded) {
-            this.subnavTarget.classList.remove(...this.hiddenClasses)
-        } else {
-            this.subnavTarget.classList.add(...this.hiddenClasses)
+        if (this.hasButtonTarget) {
+            this.buttonTarget.setAttribute('aria-expanded', expanded)
+        }
+        if (this.hasSubnavTarget) {
+            this.subnavTarget.setAttribute('aria-hidden', !expanded)
+            if (true === expanded) {
+                this.subnavTarget.classList.remove(...this.hiddenClasses)
+            } else {
+                this.subnavTarget.classList.add(...this.hiddenClasses)
+            }
         }
     }
 }