Website down after theme update

Hi, my website has gone down after updating the theme. I am getting the error

“Parse error: syntax error, unexpected ‘WP_Customize_Control’ (T_STRING) in /var/sites/d/doesshenow.co.uk/public_html/wp-content/themes/pipdig-tundra/inc/customizer.php on line 17”

I don’t know much about coding, especially Php but I’ve downloaded the theme’s php and copied and pasted it into a code checker. This is the section that’s messing things up – my untrained eye can’t spot a mistake – can anybody help me?

$dropdown = str_replace( '<select', '<select<?php
if (class_exists('WP_Customize_Control')) {
    class WP_Customize_Category_Control extends WP_Customize_Control {
        public function render_content() {
            $dropdown = wp_dropdown_categories(
                array(
                    'name'              => '_customize-dropdown-categories-' . $this->id,
                    'echo'              => 0,
                    'show_option_none'  => 'All categories',
                    'option_none_value' => '',
                    'selected'          => $this->value(),
                )
            );