fix(vue): going back to a tabs outlet no loger causes classList error (#24665)

resolves #24654

packages/vue/test-app/src/main.ts

@@ -23,10 +23,24 @@ import '@ionic/vue/css/display.css';
 /* Theme variables */
 import './theme/variables.css';
 
+/**
+ * Vue 3 has its own error handling.
+ * Throwing errors in promises go through
+ * this handler, but Cypress does not
+ * pick up on them so tests that are meant
+ * to fail will pass. By listening for unhandledrejection
+ * we can throw an error outside of Vue that will
+ * cause the test to fail as it should.
+ * See https://github.com/cypress-io/cypress/issues/5385#issuecomment-547642523
+ */
+window.addEventListener('unhandledrejection', (err) => {
+  throw new Error(err.reason);
+});
+
 const app = createApp(App)
   .use(IonicVue)
   .use(router);
-  
+
 router.isReady().then(() => {
   app.mount('#app');
-});
+});