Check if the dialog is currently open.
Examples
sample
<div id="dialog" style="display: none">Lorem ipsum dolor sit amet, consectetur adipiscing elit...</div>
<button onclick="dialog.open()" class="gj-button-md">Open Dialog</button>
<button onclick="dialog.close()" class="gj-button-md">Close Dialog</button>
<button onclick="alert($('#dialog').dialog('isOpen'))" class="gj-button-md">isOpen</button>
<script>
var dialog = $('#dialog').dialog();
</script>