Attach (recommended) or Link to PDF file here:
issue13500 (in test corpus)

This regressed when landing #13566. 

What is the expected behavior? (add screenshot)
<img width="664" alt="image" src="https://user-images.githubusercontent.com/942640/122467522-7bc8aa80-cf6f-11eb-9d4d-311eb7c64fb2.png">


What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/942640/122467565-85eaa900-cf6f-11eb-9c10-8a8686ed440c.png)


constructor(attributes) {
    super(TEMPLATE_NS_ID, "line",  true);
    this.hand = getStringOption(attributes.hand, ["even", "left", "right"]);
    this.id = attributes.id || "";
    this.slope = getStringOption(attributes.slope, ["\\", "/"]);
    this.use = attributes.use || "";
    this.usehref = attributes.usehref || "";
    this.edge = null;
  }
  [$toHTML]() {
    const parent = this[$getParent]()[$getParent]();
    const edge = this.edge ? this.edge : new Edge({});
    const edgeStyle = edge[$toStyle]();
    const style = Object.create(null);
    const thickness =
      edge.presence === "visible" ? Math.round(edge.thickness) : 0;
    style.strokeWidth = measureToString(thickness);
    style.stroke = edgeStyle.color;
    let x1, y1, x2, y2;
    let width = "100%";
    let height = "100%";
    if (parent.w <= thickness) {
      [x1, y1, x2, y2] = ["50%", 0, "50%", "100%"];
      width = style.strokeWidth;
    } else if (parent.h <= thickness) {
      [x1, y1, x2, y2] = [0, "50%", "100%", "50%"];
      height = style.strokeWidth;
    } else {
      if (this.slope === "\\") {
        [x1, y1, x2, y2] = [0, 0, "100%", "100%"];