Attach (recommended) or Link to PDF file here:
http://education.ohio.gov/getattachment/Topics/Special-Education/Preschool-Special-Education/ETR-Preschool-Planning-Form.pdf.aspx

- Web browser and its version: Firefox 89.0.1
- Operating system and its version: Windows 10 10.0.19043.1052
- PDF.js version: commit 5d251a3a3e7bfaa8fbfa07f0b7f9901eb3f999d9
- Is a browser extension: No

Steps to reproduce the problem:
1. Enable XFA support
2. Open form

What is the expected behavior? (add screenshot)
Shapes stay inside table cells
![image](https://user-images.githubusercontent.com/7104454/122572782-1252a580-d01c-11eb-9d0f-5fed46d6f2fe.png)

What went wrong? (add screenshot)
Shapes fall outside cells (among other issues)
![image](https://user-images.githubusercontent.com/7104454/122572885-2d251a00-d01c-11eb-8863-fa3b9969f0ea.png)

startIndex = 0;
        if (leader) {
          htmlContentAreas[i].children.push(leader[$toHTML](space).html);
          leader = null;
        }
        if (trailer) {
          htmlContentAreas[i].children.push(trailer[$toHTML](space).html);
          trailer = null;
        }
        const html = root[$toHTML](space);
        if (html.success) {
          if (html.html) {
            hasSomething =
              hasSomething ||
              (html.html.children && html.html.children.length !== 0);
            htmlContentAreas[i].children.push(html.html);
          } else if (!hasSomething) {
            mainHtml.children.pop();
          }
          return mainHtml;
        }
        if (html.isBreak()) {
          const node = html.breakNode;
          flush(i);
          if (node.targetType === "auto") {
            continue;
          }
          if (node.leader) {
            leader = this[$searchNode](node.leader, node[$getParent]());
            leader = leader ? leader[0] : null;