Fix subscription npe in app service creation basic panel (#4735)

Author: Flanker32

PluginsAndFeatures/azure-toolkit-for-intellij/src/com/microsoft/azure/toolkit/intellij/appservice/AppNameInput.java

@@ -44,7 +44,7 @@ public AzureValidationInfo doValidateValue() {
         final AzureValidationInfo info = super.doValidateValue();
         if (info == AzureValidationInfo.OK) {
             try {
-                ValidationUtils.validateAppServiceName(this.subscription.subscriptionId(), this.getValue());
+                ValidationUtils.validateAppServiceName(subscription != null ? subscription.subscriptionId() : null, this.getValue());
             } catch (final IllegalArgumentException e) {
                 final AzureValidationInfo.AzureValidationInfoBuilder builder = AzureValidationInfo.builder();
                 return builder.input(this).message(e.getMessage()).type(AzureValidationInfo.Type.ERROR).build();

PluginsAndFeatures/azure-toolkit-for-intellij/src/com/microsoft/azure/toolkit/intellij/appservice/AppServiceInfoBasicPanel.java

@@ -65,6 +65,8 @@ public class AppServiceInfoBasicPanel<T extends AppServiceConfig> extends JPanel
     private TitledSeparator deploymentTitle;
     private JLabel deploymentLabel;
 
+    private Subscription subscription;
+
     public AppServiceInfoBasicPanel(final Project project, final Supplier<T> defaultConfigSupplier) {
         super();
         this.project = project;
@@ -74,7 +76,9 @@ public AppServiceInfoBasicPanel(final Project project, final Supplier<T> default
     }
 
     private void init() {
+        this.subscription = AzureMvpModel.getInstance().getSelectedSubscriptions().get(0);
         this.textName.setRequired(true);
+        this.textName.setSubscription(subscription);
         this.selectorPlatform.setRequired(true);
 
         this.selectorApplication.setFileFilter(virtualFile -> {
@@ -109,7 +113,6 @@ public T getData() {
 
     private T initConfig() {
         final String appName = String.format("app-%s-%s", this.project.getName(), DATE_FORMAT.format(new Date()));
-        final Subscription subscription = AzureMvpModel.getInstance().getSelectedSubscriptions().get(0);
         final DraftResourceGroup group = DraftResourceGroup.builder().build();
         group.setName(StringUtils.substring(String.format("rg-%s", appName), 0, RG_NAME_MAX_LENGTH));
         group.setSubscription(subscription);