GETWA_NOT_ASSIGNED_RANGE

DEAR GURUS,

I am getting a runtime error GETWA_NOT_ASSIGNED_RANGE in a function module. The code extraction is in the below.

Please provide me a solution.

IT IS IN ECC 6.0.

code extraction is below:-

LOOP AT loc_detail.

ASSIGN loc_str+loc_detail-offset(loc_detail-leng) TO <fsvar>.

CONCATENATE 'INT_DATA_' loc_tab INTO fs_string-table.

MOVE '-' TO fs_string-hy.

MOVE loc_detail-fieldname TO fs_string-field.

CONDENSE fs_string NO-GAPS.

ASSIGN (fs_string) TO <fsvar1>.

runtime error >>>>>MOVE <fsvar> TO <fsvar1>.

ENDLOOP.

Please help me.

Thanks