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)


stats: task.stats.times,
      });
      this._send("/submit_task_results", result, callback);
    },
    _send: function Driver_send(url, message, callback) {
      var self = this;
      var r = new XMLHttpRequest();
      r.open("POST", url, true);
      r.setRequestHeader("Content-Type", "application/json");
      r.onreadystatechange = function (e) {
        if (r.readyState === 4) {
          self.inFlightRequests--;
          
          if (r.status !== 200) {
            setTimeout(function () {
              self._send(url, message);
            });
          }
          if (callback) {
            callback();
          }
        }
      };
      this.inflight.textContent = this.inFlightRequests++;
      r.send(message);
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  };
  return Driver;
})();