Object reference not set to an instance of an object.

Hey guys, i have a problem;
 i have the following few lines below in my codes....
FormViewRow fv3 = fvMailingAdd.Row;

Label mailingAddLabel = (Label)fvMailingAdd.FindControl("mailingAddLabel ");

 
string mailingAdd= mailingAddLabel.Text;string newMailingAdd = Convert.ToString(mailingAdd);
newMailingAdd = mailingAddLabel.Text.ToString();

labelShipTo.Text = newMailingAdd;