Hi Vishnu.
Please find logic and other details in PFA.
I have checked for Location with IfWithoutElse boolean function and given source and target fileds as accordingly but since "ns1:MT_SENDER_MULTI_MAP" itself don't contain any value so target filed is coming as "".
You can add values in the test xml, just go to mapping test tab, select generate instance and then add the values there.
Regards,
Mark