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)

const bbox = computeBbox(this, html, availableSpace);
    const ui = this.ui ? this.ui[$toHTML]().html : null;
    if (!ui) {
      Object.assign(style, borderStyle);
      return HTMLResult.success(createWrapper(this, html), bbox);
    }
    if (this[$tabIndex]) {
      if (ui.children && ui.children[0]) {
        ui.children[0].attributes.tabindex = this[$tabIndex];
      } else {
        ui.attributes.tabindex = this[$tabIndex];
      }
    }
    if (!ui.attributes.style) {
      ui.attributes.style = Object.create(null);
    }
    if (this.ui.button) {
      Object.assign(ui.attributes.style, borderStyle);
    } else {
      Object.assign(style, borderStyle);
    }
    children.push(ui);
    if (this.value) {
      if (this.ui.imageEdit) {
        ui.children.push(this.value[$toHTML]().html);
      } else if (!this.ui.button) {
        let value = "";
        if (this.value.exData) {
          value = this.value.exData[$text]();
        } else {