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)


return (
      this.hasOwnProperty(value[$nodeName]) &&
      this[value[$nodeName]].children.some(
        node => node[$content] === value[$content]
      )
    );
  }
  [$toHTML]() {
    const output = [];
    for (const child of this[$getChildren]()) {
      output.push(child[$text]());
    }
    return HTMLResult.success(output);
  }
}
class Keep extends XFAObject {
  constructor(attributes) {
    super(TEMPLATE_NS_ID, "keep",  true);
    this.id = attributes.id || "";
    const options = ["none", "contentArea", "pageArea"];
    this.intact = getStringOption(attributes.intact, options);
    this.next = getStringOption(attributes.next, options);
    this.previous = getStringOption(attributes.previous, options);
    this.use = attributes.use || "";
    this.usehref = attributes.usehref || "";
    this.extras = null;
  }
}
class KeyUsage extends XFAObject {