Attach (recommended) or Link to PDF file here:
PDF from #4106, https://mail.gnome.org/archives/evince-list/2013-November/pdfNC0hkVW67a.pdf.

Steps to reproduce the problem:
1. Open the PDF

What is the expected behavior?
![immagine](https://user-images.githubusercontent.com/1616846/121865567-67ca4200-ccfe-11eb-8673-1d6e863fc8d5.png)

What went wrong?
The PDF doesn't load, `TypeError: can't access property Symbol(), match is null` error is logged in the console.
if (this.h === "") {
      style.height = measureToString(this[$extra].height + marginV);
    }
    const html = {
      name: "div",
      attributes,
      children,
    };
    let bbox;
    if (this.w !== "" && this.h !== "") {
      bbox = [this.x, this.y, this.w, this.h];
    } else {
      const width = this.w === "" ? marginH + this[$extra].width : this.w;
      const height = this.h === "" ? marginV + this[$extra].height : this.h;
      bbox = [this.x, this.y, width, height];
    }
    if (this.breakAfter.children.length >= 1) {
      const breakAfter = this.breakAfter.children[0];
      getRoot(this)[$break](breakAfter);
      this[$extra].afterBreakAfter = HTMLResult.success(
        createWrapper(this, html),
        bbox
      );
      return HTMLResult.FAILURE;
    }
    delete this[$extra];
    return HTMLResult.success(createWrapper(this, html), bbox);
  }
}
class SubformSet extends XFAObject {