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, "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 {