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) {
      return HTMLResult.success({
        name: "div",
        children: [],
      });
    }
    this[$extra] = {
      overflowNode: null,
      firstUnsplittable: null,
      currentContentArea: null,
      currentPageArea: null,
      noLayoutFailure: false,
      pageNumber: 1,
      pagePosition: "first",
      oddOrEven: "odd",
      blankOrNotBlank: "nonBlank",
    };
    const root = this.subform.children[0];
    root.pageSet[$cleanPage]();
    const pageAreas = root.pageSet.pageArea.children;
    const mainHtml = {
      name: "div",
      children: [],
    };
    let pageArea = null;
    let breakBefore = null;
    let breakBeforeTarget = null;
    if (root.breakBefore.children.length >= 1) {
      breakBefore = root.breakBefore.children[0];