Yes, this syntax error prevents the server behavior from opening. We will be coming out with an update to address this bug after the holidays.
In the meantime I think you can probably update it to:
$RecipArray[$CurIndex] = "";
and that will allow you to open the email server behavior and set the to address to:
<?php echo ((isset($_SESSION["eCartCheckoutForm_firstname"]))?$_SESSION["eCartCheckoutForm_firstname"]:"") ?>
We also have a beta version of eCart that you can download that will produce the correct code from the wizard.