t0str

It seems that I solved the problem.

I’m supprised that it was a thing that I didn’t even think about – updating the PHP interpreter on the server to 5.6. So @maxvaehling maybe you should try doing it too when you’ll have the chance.

Anyway, thanks everyone for their support!

The 500 Internal Server Error appears regardless of the active theme (I checked it with both Storefront and TwentySeventeen) and it wont go away until i manually disable the WooCommerce plugin.

The line 30 of the file is this:
$this->wc_cart_url = esc_url( WC()->cart->get_cart_url() );

I don’t know if this will help, but this is how the entire function looks (lines 14 to 33 of the file):

    public function __construct( $model ) {
        parent::__construct( $model);

        //This filter should be added once only.
        //There might be various instances of this object but we don't want it to be added more than once
        if ( empty( self::$_woocart_filter_added ) ) {
            self::$_woocart_filter_added = true;
            add_filter( 'woocommerce_add_to_cart_fragments', array( $this, 'czr_fn_woocommerce_add_to_cart_fragment' ) );
        }

        // fix for: https://github.com/presscustomizr/customizr/issues/1223
        // WC_Cart::get_cart_url is <strong>deprecated</strong> since version 2.5! Use wc_get_cart_url instead.
        //
        if ( function_exists( 'wc_get_cart_url' ) ) {
            $this->wc_cart_url = esc_url( wc_get_cart_url() );
        } else {
            $this->wc_cart_url = esc_url( WC()->cart->get_cart_url() );
        }

    }