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)


this.dataColumnCount = getInteger({
      data: attributes.dataColumnCount,
      defaultValue: -1,
      validate: x => x >= 0,
    });
    this.dataLength = getInteger({
      data: attributes.dataLength,
      defaultValue: -1,
      validate: x => x >= 0,
    });
    this.dataPrep = getStringOption(attributes.dataPrep, [
      "none",
      "flateCompress",
    ]);
    this.dataRowCount = getInteger({
      data: attributes.dataRowCount,
      defaultValue: -1,
      validate: x => x >= 0,
    });
    this.endChar = attributes.endChar || "";
    this.errorCorrectionLevel = getInteger({
      data: attributes.errorCorrectionLevel,
      defaultValue: -1,
      validate: x => x >= 0 && x <= 8,
    });
    this.id = attributes.id || "";
    this.moduleHeight = getMeasurement(attributes.moduleHeight, "5mm");
    this.moduleWidth = getMeasurement(attributes.moduleWidth, "0.25mm");
    this.printCheckDigit = getInteger({
      data: attributes.printCheckDigit,