Fixed track shipment smoke test failure on IFRC, Default and SandyRelief

There was a smoke test failure on this url http://127.0.0.1:8000/eden/inv/track_movement?viewing=inv_item.None for the default, IFRC and SandyRelief templates as can be seen on the test report http://82.71.213.53/RESULTS/SMOKE/default/Sahana-Eden-2013-10-05%2002-17-04.537158.html

Handled the case where the whole shipment was being tracked and the item_id was set to None.