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)


return parent[$getNextPage]();
      }
      this[$cleanPage]();
      return this[$getNextPage]();
    }
    const pageNumber = this[$getTemplateRoot]()[$extra].pageNumber;
    const parity = pageNumber % 2 === 0 ? "even" : "odd";
    const position = pageNumber === 0 ? "first" : "rest";
    let page = this.pageArea.children.find(
      p => p.oddOrEven === parity && p.pagePosition === position
    );
    if (page) {
      return page;
    }
    page = this.pageArea.children.find(
      p => p.oddOrEven === "any" && p.pagePosition === position
    );
    if (page) {
      return page;
    }
    page = this.pageArea.children.find(
      p => p.oddOrEven === "any" && p.pagePosition === "any"
    );
    if (page) {
      return page;
    }
    return this.pageArea.children[0];
  }
}
class Para extends XFAObject {