unable to invoke scheduleService from Object function

Content

We are using a scheduleService SOAP webservice for schedule Report but unable to call the same from groovy object function with a working payload from SOAPUI. The payload is : https://cccl-test.fa.us2.oraclecloud.com/xmlpserver/services/v2/ScheduleService?WSDL

The error that we are getting is :

Exception in expression "ProgramApprovalInitiate_c" object function getSyncQualifiers() : java.lang.NullPointerException : Cannot invoke method scheduleReport() on null object
at "ProgramApprovalInitiate_c" object function getSyncQualifiers() line 189

where line 189 is the webservice invocation line.

Attached is the groovy script. 

Also, while reading the WSDL there is a warning message :

"The preferred security options could not be determined. Contact your web service provider or consult your web service documentation to obtain the correct security details. If errors occur during service invocation, contact your system administrator with the web service and error details.