[FIX] point of sale: order undefined

If the line is linked to an order, this line must be removed in this order.

addons/point_of_sale/static/src/js/models.js

@@ -1051,7 +1051,7 @@ function openerp_pos_models(instance, module){ //module is instance.point_of_sal
         },
         addOrderline: function(line){
             if(line.order){
-                order.removeOrderline(line);
+                line.order.removeOrderline(line);
             }
             line.order = this;
             this.get('orderLines').add(line);