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)


delete this[$extra];
  }
  [$getNextPage]() {
    if (!this[$extra]) {
      this[$extra] = {
        numberOfUse: 0,
      };
    }
    const parent = this[$getParent]();
    if (parent.relation === "orderedOccurrence") {
      if (this[$isUsable]()) {
        this[$extra].numberOfUse += 1;
        return this;
      }
    }
    return parent[$getNextPage]();
  }
  [$getAvailableSpace]() {