X Icon not showing

Site URL: https://wisteria-triangle-r9ms.squarespace.com

Hi there I am hoping someone could assist — on my mobile site, the 'X' icon is hidden when the navigation burger icon is clicked, if anyone could assit me in making the 'X' white/visable that would be fantatsic.

Thanks in advance

Add to Home > Design > Custom CSS

.burger-inner>div {
    background: white !important;
}