Jobs number in cart is wrong

Adding Items to the cart will increase the cart jobs count while emptying the cart or removing items from the cart will not decrease the total number displayed.

I tracked this issue and found the following.

The constructor is assigning the SESSION to the cart variable by reference.
Emptying the cart will remove this reference by assigning a new empty array to the cart variable which will make it impossible at this case to update the values stored in the session.

<?php
protected function __construct() {
  if (!isset($_SESSION[$this->session_key])) {
    $_SESSION[$this->session_key] = array();
  }
  $this->cart = &$_SESSION[$this->session_key];
}
?>

<?php
public function emptyCart() {
  $this->cart = array();
}
?>

I recommend using manipulating the SESSION values directly without using a reference.