:ERROR MESSAGE:
org.ofbiz.widget.screen.ScreenRenderException: Error rendering screen [component://flow/widget/flow/flow.xml#createBill]: java.lang.IllegalArgumentException: Error running script at location [component://flow/webapp/flow/WEB-INF/actions/createBill.groovy]: java.lang.NullPointerException: Cannot get property 'headEntityName' on null object (Error running script at location [component://flow/webapp/flow/WEB-INF/actions/createBill.groovy]: java.lang.NullPointerException: Cannot get property 'headEntityName' on null object)