Apply suggestions from code review

Co-Authored-By: Vlad Rindevich <[email protected]>

Author: johannalee

README.md

@@ -84,7 +84,7 @@ function* treeWalker(refresh) {
     const isOpened = yield refresh
       ? {
           id,
-          isLeaf: children?.length === 0,
+          isLeaf: !children || children.length === 0,
           isOpenByDefault: true,
           name,
           nestingLevel,
@@ -93,7 +93,7 @@ function* treeWalker(refresh) {
 
     // Basing on the node openness state we are deciding if we need to render
     // the child nodes (if they exist).
-    if (children?.length !== 0 && isOpened) {
+    if (children && children.length > 0 && isOpened) {
       // Since it is a stack structure, we need to put nodes we want to render
       // first to the end of the stack.
       for (let i = children?.length - 1; i >= 0; i--) {
@@ -253,7 +253,7 @@ function* treeWalker(refresh) {
           // object.
           defaultHeight: 30,
           id,
-          isLeaf: children?.length === 0,
+          isLeaf: !children || children.length === 0,
           isOpenByDefault: true,
           name,
           nestingLevel,