Attach (recommended) or Link to PDF file here:
[docOficialPDF.php.pdf](https://github.com/mozilla/pdf.js/files/7159923/docOficialPDF.php.pdf)

Configuration:
- Web browser and its version: Firefox nightly
- Operating system and its version: linux debian
- PDF.js version: built-in viewer
- Is a browser extension: no

Steps to reproduce the problem:
1. Open the pdf page 2
2. Checkbox "Alta" in section 2 must be checked

It works fine with evince.
selectElement.multiple = true;
          },
          remove(event) {
            const options = selectElement.options;
            const index = event.detail.remove;
            options[index].selected = false;
            selectElement.remove(index);
            if (options.length > 0) {
              const i = Array.prototype.findIndex.call(
                options,
                option => option.selected
              );
              if (i === -1) {
                options[0].selected = true;
              }
            }
            storage.setValue(id, {
              value: getValue(event,  true),
              items: getItems(event),
            });
          },
          clear(event) {