Remove cart dependency from uc_payment

In uc_payment.module, line: 457 uc_payment_enter(..) there is a call to uc_cart_complete_sale($order);

uc_payment.module does not list uc_cart as a dependency, and to be fair - it shouldn't necessarily be dependent. For example, we are using the order module to proxy transactions through another gateway without using the cart.

I propose the following change:

   $order = uc_order_load($order_id, TRUE);
   $account = user_load($uid);
    
  // Ensure user has an account before payment is made.
  
  if (module_exists("uc_cart")){
      uc_cart_complete_sale($order);
  }