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)


}
        }
        if (this.ui.textEdit && this.value.text && this.value.text.maxChars) {
          ui.children[0].attributes.maxLength = this.value.text.maxChars;
        }
        if (value) {
          if (ui.children[0].name === "textarea") {
            ui.children[0].attributes.textContent = value;
          } else {
            ui.children[0].attributes.value = value;
          }
        }
      }
    }
    const caption = this.caption ? this.caption[$toHTML]().html : null;
    if (!caption) {
      if (ui.attributes.class) {
        
        ui.attributes.class.push("xfaLeft");
      }
      return HTMLResult.success(createWrapper(this, html), bbox);
    }
    if (this.ui.button) {
      if (caption.name === "div") {
        caption.name = "span";
      }
      ui.children.push(caption);
      return HTMLResult.success(html, bbox);
    } else if (this.ui.checkButton) {
      caption.attributes.class[0] = "xfaCaptionForCheckButton";