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)


textLayerCanvas.height
                );
                var enhanceText = !!task.enhance;
                
                initPromise = page
                  .getTextContent({
                    normalizeWhitespace: true,
                    includeMarkedContent: true,
                  })
                  .then(function (textContent) {
                    return rasterizeTextLayer(
                      textLayerContext,
                      viewport,
                      textContent,
                      enhanceText
                    );
                  });
              } else {
                textLayerCanvas = null;
                
                
                renderAnnotations = !!task.annotations;
                renderForms = !!task.forms;
                renderPrint = !!task.print;
                renderXfa = !!task.enableXfa;
                
                if (renderAnnotations || renderForms || renderXfa) {
                  
                  annotationLayerCanvas = self.annotationLayerCanvas;
                  if (!annotationLayerCanvas) {