Attach (recommended) or Link to PDF file here:
[imm5710f(1).pdf](https://github.com/mozilla/pdf.js/files/6924738/imm5710f.1.pdf)

Configuration:
- Web browser and its version: Firefox nightly
- Operating system and its version: Debian

Steps to reproduce the problem:
1. Open the pdf on page 3 
2. See the 2 fields after `DÉTAILS DU TRAVAIL PRÉVU AU CANADA`

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/128031365-84b17d62-f805-43d1-9d05-e2b535efa3ef.png)

if (!node[$extra]) {
    return null;
  }
  const attributes = node[$extra].attributes;
  const html = {
    name: "div",
    attributes,
    children: node[$extra].children,
  };
  if (node[$extra].failingNode) {
    const htmlFromFailing = node[$extra].failingNode[$flushHTML]();
    if (htmlFromFailing) {
      if (node.layout.endsWith("-tb")) {
        html.children.push(createLine(node, [htmlFromFailing]));
      } else {
        html.children.push(htmlFromFailing);
      }
    }
  }
  if (html.children.length === 0) {
    return null;
  }
  return html;
}
function addHTML(node, html, bbox) {