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)


static [$buildXFAObject](name, attributes) {
    if (TemplateNamespace.hasOwnProperty(name)) {
      const node = TemplateNamespace[name](attributes);
      node[$setSetAttributes](attributes);
      return node;
    }
    return undefined;
  }
  static appearanceFilter(attrs) {
    return new AppearanceFilter(attrs);
  }
  static arc(attrs) {
    return new Arc(attrs);
  }
  static area(attrs) {
    return new Area(attrs);
  }
  static assist(attrs) {
    return new Assist(attrs);
  }
  static barcode(attrs) {
    return new Barcode(attrs);
  }
  static bind(attrs) {
    return new Bind(attrs);
  }
  static bindItems(attrs) {
    return new BindItems(attrs);
  }
  static bookend(attrs) {