Hide optional groups when no optional groups are selected.

hide_optional_groups.html

<!-- BEGIN script to hide optional groups prompt when there are no optional groups. -->
<script type="text/javascript">
  document.addEventListener("DOMContentLoaded", () => {
    var e = document.querySelector("#salsa-optional-groups-header")
    if (e != null) {
        var f = document.querySelectorAll("li.salsa-optional-group")
        if (f.length == 0) {
        e.style.display = "None"
        }
    }
  });
</script>
<!-- END   script to hide optional groups prompt when there are no optional groups. -->