Display avatar of user profile when logged in

I am trying to display user’s avatar/profile image when logged in, but when I use this:

 <?php
    global $current_user;
    get_currentuserinfo();     
    echo get_avatar( $current_user->ID, 64 );

?>

it displays the default_avatar_male.jpg, but I don’t want anything to be displayed unless logged in. Thanks for all help.