Uncaught TypeError: Cannot read property ‘className’ of null

I am so new at debugging so I don’t know what can I provide as more information. Can you look at the problem and my website.

to solve it, I disable customize support from function.php, but it didn’t solve.

Homepage Bclinico

<script type="text/javascript">
        (function() {
            var request, b = document.body, c = 'className', cs = 'customize-support', rcs = new RegExp('(^|\s+)(no-)?'+cs+'(\s+|$)');

                request = true;
    
            b(c) = b(c).replace( rcs, ' ' );
            // The customizer requires postMessage and CORS (if the site is cross domain).
            b(c) += ( window.postMessage && request ? ' ' : ' no-' ) + cs;
        }());
    </script>