This should fix https://issues.apache.org/jira/browse/OFBIZ-2574 "Not possible to show the shipment information (packaging slip) in the purchase order approvement screen"

See Purchase Order #DEMO10090 in the Order Managaer application, where the order are to be approved.

Try to click on the link; 
Shipments    Nbr 9998  Packing Slip 

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Then the following error is shown:
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The Following Errors Occurred:

Problems with the response writer/output stream: org.ofbiz.widget.screen.ScreenRenderException: Error rendering screen [component://product/widget/facility/ShipmentScreens.xml#PackingSlip.fo]: java.lang.IllegalArgumentException: Operator must be EQUALS or NOT_EQUAL when right/rhs argument is NULL (Operator must be EQUALS or NOT_EQUAL when right/rhs argument is NULL )
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git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1512376 13f79535-47bb-0310-9956-ffa450edef68