fix issue with cached data in session storage of demo app

Author: tanguyenvn

demo/vue-app-new/src/MainView.vue

@@ -211,7 +211,7 @@ onBeforeMount(() => {
         formData.network = json.network;
         formData.whiteLabel = json.whiteLabel;
         formData.walletPlugin = json.walletPlugin;
-        formData.nftCheckoutPlugin = json.nftCheckoutPlugin;
+        formData.nftCheckoutPlugin = json.nftCheckoutPlugin || {};
         formData.useAccountAbstractionProvider = json.useAccountAbstractionProvider;
         formData.smartAccountType = json.smartAccountType;
         formData.bundlerUrl = json.bundlerUrl;