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)

constructor(parameters) {
    super(parameters);
    this.data.annotationType = AnnotationType.POPUP;
    let parentItem = parameters.dict.get("Parent");
    if (!parentItem) {
      warn("Popup annotation has a missing or invalid parent annotation.");
      return;
    }
    const parentSubtype = parentItem.get("Subtype");
    this.data.parentType = isName(parentSubtype) ? parentSubtype.name : null;
    const rawParent = parameters.dict.getRaw("Parent");
    this.data.parentId = isRef(rawParent) ? rawParent.toString() : null;
    const parentRect = parentItem.getArray("Rect");
    if (Array.isArray(parentRect) && parentRect.length === 4) {
      this.data.parentRect = Util.normalizeRect(parentRect);
    } else {
      this.data.parentRect = [0, 0, 0, 0];
    }
    const rt = parentItem.get("RT");
    if (isName(rt, AnnotationReplyType.GROUP)) {