What does this message mean? The rest of the warning says

Line 64 in /var/www/mysite/ecommerce/code/forms/fields/EcomQuantityField.php

Source

55          if(!$this->orderItem) {
56             $className = $object->classNameForOrderItem();
57             $this->orderItem = new $className($object->dataRecord,0);
58          }
59       }
60       elseif($object instanceof OrderItem && $object->BuyableID){
61          $this->orderItem = $object;
62       }
63       else{
64          user_error("EcomQuantityField: no/bad order item or buyable passed to constructor.", E_USER_WARNING);
65       }
66       $this->parameters = $parameters;
67    }
68
69    function setClasses($newclasses, $overwrite = false){
70       if($overwrite) {

and then there's the trace.

I'm guessing it's some sort of config issue, but where?

Can anybody help with this?