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.
constructor(attributes) {
    super(TEMPLATE_NS_ID, "linear",  true);
    this.id = attributes.id || "";
    this.type = getStringOption(attributes.type, [
      "toRight",
      "toBottom",
      "toLeft",
      "toTop",
    ]);
    this.use = attributes.use || "";
    this.usehref = attributes.usehref || "";
    this.color = null;
    this.extras = null;
  }
  [$toStyle](startColor) {
    startColor = startColor ? startColor[$toStyle]() : "#FFFFFF";
    const transf = this.type.replace(/([RBLT])/, " $1").toLowerCase();
    const endColor = this.color ? this.color[$toStyle]() : "#000000";
    return `linear-gradient(${transf}, ${startColor}, ${endColor})`;
  }
}
class LockDocument extends ContentObject {