Hello,
For a reason I'm not able to connect via ftp... But I analyze your cart.php with your modification and I find maybe the error.
From your code, you have remove a condition :
if($product->product_id == $characteristic->variant_product_id) {
just after the
foreach($characteristics as $characteristic) {
it's around line
992 That may explain your error, you have to see this :
foreach($characteristics as $characteristic) {
if($product->product_id == $characteristic->variant_product_id) {
/* Adjustment Nicolas */
if($product->product_type === 'variant') {
if(empty($product->characteristics))
$product->characteristics = array();
$product->characteristics[] = $characteristic;
} else {
if(empty($mainCharacteristics[$product->product_id]))
$mainCharacteristics[$product->product_id] = array();
if(empty($mainCharacteristics[$product->product_id][$characteristic->characteristic_parent_id]))
$mainCharacteristics[$product->product_id][$characteristic->characteristic_parent_id] = array();
$mainCharacteristics[$product->product_id][$characteristic->characteristic_parent_id][$characteristic->characteristic_id] = $characteristic;
}
/* End Adjustment Nicolas */
Screenshot review :
Hope this will help you to move forward.
Regards