Attach (recommended) or Link to PDF file here:
https://guichet.public.lu/dam-assets/catalogue-formulaires/tva/tva-option-aic-pers-morales/tva-option-aic-pers-morale-DE.pdf

Configuration:
- Web browser and its version: Firefox Nightly 91.0a1 (2021-06-26) (64-bit)
- Operating system and its version: Windows 10.0.19043.1052
- PDF.js version: N/A

Steps to reproduce the problem:
1. enableXFA in Firefox Nightly
2. Open form

What is the expected behavior? (add screenshot)
Header image is scaled properly
![image](https://user-images.githubusercontent.com/7104454/123525954-905d1f00-d6a2-11eb-840e-be30eee395e1.png)

What went wrong? (add screenshot)
Image is scaled to fit
![image](https://user-images.githubusercontent.com/7104454/123525957-96530000-d6a2-11eb-9991-bf7f37c6f1a5.png)


classNames.push("xfaPrintOnly");
    }
    const attributes = {
      style,
      id: this[$uid],
      class: classNames,
    };
    if (this.name) {
      attributes.xfaName = this.name;
    }
    const html = {
      name: "div",
      attributes,
      children: [],
    };
    const bbox = computeBbox(this, html, availableSpace);
    const value = this.value ? this.value[$toHTML](availableSpace).html : null;
    if (value === null) {
      return HTMLResult.success(createWrapper(this, html), bbox);
    }
    html.children.push(value);
    if (value.attributes.class && value.attributes.class.includes("xfaRich")) {
      if (this.h === "") {
        style.height = "auto";
      }
      if (this.w === "") {
        style.width = "auto";
      }
      if (this.para) {