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)

if (data.fieldType === "Sig") {
      data.fieldValue = null;
      this.setFlags(AnnotationFlag.HIDDEN);
      data.hidden = true;
    }
  }
  /**
   * Construct the (fully qualified) field name from the (partial) field
   * names of the field and its ancestors.
   *
   * @private
   * @memberof WidgetAnnotation
   * @param {Dict} dict - Complete widget annotation dictionary
   * @returns {string}
   */
  _constructFieldName(dict) {
    
    
    if (!dict.has("T") && !dict.has("Parent")) {
      warn("Unknown field name, falling back to empty field name.");
      return "";
    }
    
    if (!dict.has("Parent")) {
      return stringToPDFString(dict.get("T"));
    }