MultiplayerFPS - database error

With the new updates of the free database assets appared this error that i can’t risolve:

NullReferenceException: Object reference not set to an instance of an object
LoginMenu+c__Iterator0.MoveNext () (at Assets/LoginMenu.cs:146)
UnityEngine.SetupCoroutine.InvokeMoveNext (IEnumerator enumerator, IntPtr returnValueAddress) (at C:/buildslave/unity/build/Runtime/Export/Coroutines.cs:17)

That refers to:

WWW returned = e.Current as WWW;
if (returned.text == “Success”) {

Any suggestion ?

IEnumerator sendLoginRequest(string username, string password)
{

    if (isDatabaseSetup == true)
    {

        IEnumerator e = DCF.Login(username, password);
        while (e.MoveNext())
        {
            yield return e.Current;
        }
        string returned = e.Current as string;
        if (returned == "Success")
        {

            //Password was correct
            blankErrors();
            part = 2; //show logged in UI

            //blank username field
            input_login_username.text = ""; //password field is blanked at the end of this function, even when error is returned
                                            //UserAccountManager.LoggedIn_Username = username;
                                            // UserAccountManager.LoggedIn_Password = password;

            UserAccountManager.instance.LogIn(username, password);
        }
        if (returned == "incorrectUser")
        {
            //Account with username not found in database
            login_error.text = "Username not found";
            part = 0; //back to login UI
        }
        if (returned == "incorrectPass")
        {
            //Account with username found, but password incorrect
            part = 0; //back to login UI
            login_error.text = "Incorrect Password";
        }
        if (returned == "ContainsUnsupportedSymbol")
        {
            //One of the parameters contained a - symbol
            part = 0; //back to login UI
            login_error.text = "Unsupported Symbol '-'";
        }
        if (returned == "Error")
        {
            //Account Not Created, another error occurred
            part = 0; //back to login UI
            login_error.text = "Database Error. Try again later.";
        }

        //blank password field
        input_login_password.text = "";

    }
}