Clear background if content present in textarea jQuery

Question

Please see this jsFiddle: https://jsfiddle.net/Wmq6f/

I have a textarea that has a background image, it is removed on 'focus' and restored on 'blur' but when the content is present in the textarea it should not show in either case, but I can't achieve that with this jQuery:

$('textarea').focus(function() {
   var $this = $(this);
   $.data(this, 'img', $this.css('background-image'));
   $this.css('background-image', 'none');
});
$('textarea').blur(function() {
    if($.trim($('textarea').val()).length){
         $this.css('background-image', 'none');
    } else {
        $(this).css('background-image', $.data(this, 'img'));
    }
});

Thanks for your help