how to handle null

sir using ado i retrieve alues from a field like this

_ConnectionPtr con;
_RecordsetPtr rec;

con.CreateInstance(__uuidof(Conection));
con->Open() // to connect to the data source

rec.CreateInstance(__uuidof(Recordset));
rec->PutRefActiveConection(con);

rec->Open() // to open recordset using sql statement
               select emp_phone from employees

 Now this emp_phone field can contain NULL values also
 Then i use the following code to extract values from emp_phone

_variant_t v_phone;
v_phone=rec->GetCollect(L"emp_phone");

now this GetCollect() retrns value of type _variant_t which then gets stored in v_phone

then i use something like this

lstrcpy(str,(_bstr_t)v_phone)

and then i use str to show emp_phone's value

the point is that if emp_phone contains value
then lstrcpy() works fine

but if emp_phone's value is NULL
then if i use lstrcpy(str,(_bstr_t)v_phone)
the program gives error at run time
saying abnormal termination

so how should i find whether value in v_phone is null so that i dont use lstrcpy() in that case