Fix possible index out of bounds exception when select resource

Author: Flanker-MSFT

PluginsAndFeatures/azure-toolkit-for-intellij/azure-intellij-plugin-lib/src/main/java/com/microsoft/azure/toolkit/intellij/common/component/TreeUtils.java

@@ -266,10 +266,10 @@ public static boolean underTypeGroups(@Nonnull TreePath path) {
 
     public static void selectResourceNode(@Nonnull JTree tree, @Nonnull AzComponent resource) {
         final DefaultMutableTreeNode r = (DefaultMutableTreeNode) tree.getModel().getRoot();
-        DefaultMutableTreeNode root = ((DefaultMutableTreeNode) r.getChildAt(1)); // apps root
+        DefaultMutableTreeNode root = r.getChildCount() > 1 ? ((DefaultMutableTreeNode) r.getChildAt(1)) : null; // apps root
         if (resource instanceof Favorite) {
             resource = ((Favorite) resource).getResource();
-            root = (DefaultMutableTreeNode) r.getChildAt(0); // favorite root
+            root = r.getChildCount() > 0 ? (DefaultMutableTreeNode) r.getFirstChild() : null; // favorite root
         }
         if (Objects.nonNull(resource)) {
             selectResourceNode(tree, resource, root);