$('#movenextbtn').click(function(){window.location.href="https://www.example.com"});

<button class='submit' type='submit' onclick="javascript:document.limesurvey.move.value = 'movenext';

<script>
$(document).ready(function () {
    $("#movenextbtn").click(function(e){
        if($("#answer{SGQ}").val()==""){
            e.preventDefault();
            window.location.href="https://example.com";
        }else{
            // Do something other, here : default
        }
    });
});
</script>