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)

const items = field.items;
      let displayedIndex = 0;
      let saveIndex = 0;
      if (items.children.length === 2) {
        displayedIndex = items.children[0].save;
        saveIndex = 1 - displayedIndex;
      }
      const displayed = items.children[displayedIndex][$toHTML]().html;
      const values = items.children[saveIndex][$toHTML]().html;
      let selected = false;
      const value = (field.value && field.value[$text]()) || "";
      for (let i = 0, ii = displayed.length; i < ii; i++) {
        const option = {
          name: "option",
          attributes: {
            value: values[i] || displayed[i],
          },
          value: displayed[i],
        };
        if (values[i] === value) {
          option.attributes.selected = selected = true;
        }
        children.push(option);
      }
      if (!selected) {
        children.splice(0, 0, {
          name: "option",
          attributes: {
            hidden: true,
            selected: true,