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)


pdfjsLib.GlobalWorkerOptions.workerSrc = WORKER_SRC;
    
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    this.end = options.end;
    
    var parameters = this._getQueryStringParameters();
    this.browser = parameters.browser;
    this.manifestFile = parameters.manifestFile;
    this.delay = parameters.delay | 0 || 0;
    this.inFlightRequests = 0;
    this.testFilter = parameters.testFilter
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    this.canvas = document.createElement("canvas");
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  Driver.prototype = {
    _getQueryStringParameters: function Driver_getQueryStringParameters() {
      var queryString = window.location.search.substring(1);
      var values = queryString.split("&");
      var parameters = {};
      for (var i = 0, ii = values.length; i < ii; i++) {
        var value = values[i].split("=");
        parameters[unescape(value[0])] = unescape(value[1]);
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      return parameters;
    },