When uploading a pdf file, I get Warning: Unimplemented widget field type "null", falling back to base field type at pdf.worker.js. The file is not loading.
I'm using the chrome browser. All other files are processed fine, but this one is not. Help solve the problem.
[usn2020.pdf](https://github.com/mozilla/pdf.js/files/5936611/usn2020.pdf)

return this.appearance.dict.getAsync("Resources").then(resources => {
      if (!resources) {
        return undefined;
      }
      const objectLoader = new ObjectLoader(resources, keys, resources.xref);
      return objectLoader.load().then(function () {
        return resources;
      });
    });
  }
  getOperatorList(evaluator, task, renderForms, annotationStorage) {
    if (!this.appearance) {
      return Promise.resolve(new OperatorList());
    }
    const appearance = this.appearance;
    const data = this.data;
    const appearanceDict = appearance.dict;
    const resourcesPromise = this.loadResources([
      "ExtGState",
      "ColorSpace",
      "Pattern",
      "Shading",
      "XObject",
      "Font",
    ]);
    const bbox = appearanceDict.getArray("BBox") || [0, 0, 1, 1];
    const matrix = appearanceDict.getArray("Matrix") || [1, 0, 0, 1, 0, 0];
    const transform = getTransformMatrix(data.rect, bbox, matrix);
    return resourcesPromise.then(resources => {
      const opList = new OperatorList();