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)


target = null;
            }
            const index = contentAreas.findIndex(e => e === target);
            if (index !== -1) {
              flush(i);
              i = index - 1;
            } else {
              i--;
            }
          }
          continue;
        }
        if (this[$extra].overflowNode) {
          const node = this[$extra].overflowNode;
          this[$extra].overflowNode = null;
          flush(i);
          if (node.leader) {
            leader = this[$searchNode](node.leader, node[$getParent]());
            leader = leader ? leader[0] : null;
          }
          if (node.trailer) {
            trailer = this[$searchNode](node.trailer, node[$getParent]());
            trailer = trailer ? trailer[0] : null;
          }
          let target = null;
          if (node.target) {
            target = this[$searchNode](node.target, node[$getParent]());
            target = target ? target[0] : target;
          }
          if (target instanceof PageArea) {