in default drop down field value how to make it first value in empty line ?

Hi team,

My requirement is Complaint header page,Category fields( its a drop down field),in this field total values 5.now it is showing default ZRP value.but we want only empty line after that user will select manually one be one.for this i have added the logic on insert line item to lt_ddlb index 1.but still it is shoing default value.how to do it.could you please help.

Component - BT120H_CPL

View - BT120H_CPL/Details

Context node - BTADMINH

Attribute - GET_V_CATEGORY

Thanks & Regards

Kalpana