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)


for (let i = 0, ii = contentAreas.length; i < ii; i++) {
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          leader = null;
        }
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          htmlContentAreas[i].children.push(trailer[$toHTML](space).html);
          trailer = null;
        }
        const html = root[$toHTML](space);
        if (html.success) {
          if (html.html) {
            hasSomething =
              hasSomething ||
              (html.html.children && html.html.children.length !== 0);
            htmlContentAreas[i].children.push(html.html);
          } else if (!hasSomething) {
            mainHtml.children.pop();
          }
          return mainHtml;
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            continue;
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          const startNew = node.startNew === 1;