Get data

Another little help please
Now that I have found my data, I want to display a button linked to the website field which contains a URL. If this field is empty I want to hide the button:
Initially the button is “hidden”

if ( liencv !== null && liencv !== ‘’ ) {
$w ( ‘#btnliencv’ ). show ();
}
else {
$w ( ‘#btnliencv’ ). hide ();
}
But I still see the button?
Whoops ! what is my mistake?