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)


breakBeforeTarget,
        breakBefore[$getParent]()
      );
      if (target instanceof PageArea) {
        pageArea = target;
        
        breakBefore[$extra] = {};
      }
    }
    if (!pageArea) {
      pageArea = pageAreas[0];
    }
    pageArea[$extra] = {
      numberOfUse: 1,
    };
    const pageAreaParent = pageArea[$getParent]();
    pageAreaParent[$extra] = {
      numberOfUse: 1,
      pageIndex: pageAreaParent.pageArea.children.indexOf(pageArea),
      pageSetIndex: 0,
    };
    let targetPageArea;
    let leader = null;
    let trailer = null;
    let hasSomething = true;
    let hasSomethingCounter = 0;
    while (true) {
      if (!hasSomething) {
        
        if (++hasSomethingCounter === MAX_EMPTY_PAGES) {