Fix to knockout sorting when dragging item index 1 to 0.

The items would not swap positions when you dragged item with index 1 to
the top of the stack at index 0.

knockout-sortable.js

@@ -84,9 +84,11 @@
                     newIndex = e.newIndex;
 
                 if (e.item.previousElementSibling)
+                {
                     newIndex = fromArray.indexOf(ko.dataFor(e.item.previousElementSibling));
                     if (originalIndex > newIndex)
                         newIndex = newIndex + 1;
+                }                
 
                 //Remove sortables "unbound" element
                 e.item.parentNode.removeChild(e.item);