Attach (recommended) or Link to PDF file here:
[0 NIF MODELO 30.pdf](https://github.com/mozilla/pdf.js/files/7187486/0.NIF.MODELO.30.2.pdf)

Configuration:
- Web browser and its version: firefox nightly
- Operating system and its version: linux debian

Steps to reproduce the problem:
1. Open the PDF
2. Click on the button  `Rellenar Formulario` (top right of the first page)
3. There is the pop-up "Stay... or Leave...`.

It's a bit annoying from the user pov and it doesn't make sense (nobody wants to leave the form but just reset it)

It works fine when replacing  `""` by `"#"` here:
https://github.com/mozilla/pdf.js/blob/7082ff9bf876b98fbda118cdbd6267d3c0df6948/src/display/annotation_layer.js#L483

@Snuffleupagus, you changed this few month ago:
https://github.com/mozilla/pdf.js/commit/e2b6d79dee9ffd2aba715d6b3cb8fa143d86153c

do you have some ideas ?
if (!event.target.multiple) {
        return options.selectedIndex === -1
          ? null
          : options[options.selectedIndex][name];
      }
      return Array.prototype.filter
        .call(options, option => option.selected)
        .map(option => option[name]);
    };
    const getItems = event => {
      const options = event.target.options;
      return Array.prototype.map.call(options, option => {
        return { displayValue: option.textContent, exportValue: option.value };
      });
    };
    if (this.enableScripting && this.hasJSActions) {
      selectElement.addEventListener("updatefromsandbox", jsEvent => {
        const actions = {
          value(event) {
            const options = selectElement.options;
            const value = event.detail.value;
            const values = new Set(Array.isArray(value) ? value : [value]);
            Array.prototype.forEach.call(options, option => {
              option.selected = values.has(option.value);
            });
            storage.setValue(id, {
              value: getValue(event,  true),
            });
          },
          multipleSelection(event) {