Attach (recommended) or Link to PDF file here:
https://www.placementsmondiauxsunlife.com/content/dam/sunlife/regional/canada/documents/slgi/4839-I-F.pdf

Configuration:

- Web browser and its version: 91.0a1 (2021-07-03) (64-bit)
- Operating system and its version: Windows 10

Steps to reproduce the problem:
1. enableXfa = true
2. Open form

What is the expected behavior? (add screenshot)

![image](https://user-images.githubusercontent.com/7104454/124389449-1ede2b80-dcb5-11eb-98ba-01e1f3d6c6f5.png)


What went wrong? (add screenshot)

![image](https://user-images.githubusercontent.com/7104454/124389460-2c93b100-dcb5-11eb-9768-98ddd2c8f1e7.png)

if (this.subform.children.length === 0) {
      warn("XFA - No subforms in template node.");
    }
    if (this.subform.children.length >= 2) {
      warn("XFA - Several subforms in template node: please file a bug.");
    }
    this[$tabIndex] = 1000;
  }
  [$isSplittable]() {
    return true;
  }
  [$searchNode](expr, container) {
    if (expr.startsWith("#")) {
      
      return [this[$ids].get(expr.slice(1))];
    }
    return searchNode(this, container, expr, true, true);
  }
  [$toHTML]() {