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)

constructor(attributes) {
    super(TEMPLATE_NS_ID, "submit",  true);
    this.embedPDF = getInteger({
      data: attributes.embedPDF,
      defaultValue: 0,
      validate: x => x === 1,
    });
    this.format = getStringOption(attributes.format, [
      "xdp",
      "formdata",
      "pdf",
      "urlencoded",
      "xfd",
      "xml",
    ]);
    this.id = attributes.id || "";
    this.target = attributes.target || "";
    this.textEncoding = getKeyword({
      data: attributes.textEncoding
        ? attributes.textEncoding.toLowerCase()
        : "",
      defaultValue: "",
      validate: k =>
        [
          "utf-8",
          "big-five",
          "fontspecific",
          "gbk",
          "gb-18030",
          "gb-2312",