Fatal error in backoffice | WordPress.org

Hello,

I can’t access some back-office features, especially the Customize tab, because I have a fatal error caused by the Twenty20 extension:

Fatal error: Uncaught Error: Call to undefined function esc_htmlesc_html_e() in ……… /wp-content/plugins/twenty20/inc/widget-twenty20.php on line 101

Can you please help me solve this problem?