We have released a new build of eCart so that this problem will no longer happen.
If you already ran into this issue and don't want to run the wizard again you should be able to replace:
$RecipArray[$CurIndex][] = $row_<?php echo ((isset($_SESSION["eCartCheckoutForm_firstname"]))?$_SESSION["eCartCheckoutForm_firstname"]:"") ?>
<?php echo ((isset($_SESSION["eCartCheckoutForm_lastname"]))?$_SESSION["eCartCheckoutForm_lastname"]:"") ?>|WA|<?php echo ((isset($_SESSION["eCartCheckoutForm_email"]))?$_SESSION["eCartCheckoutForm_email"]:"") ?>;
$RecipArray[$CurIndex][] = $<?php echo ((isset($_SESSION["eCartCheckoutForm_firstname"]))?$_SESSION["eCartCheckoutForm_firstname"]:"") ?><?php echo ((isset($_SESSION["eCartCheckoutForm_lastname"]))?$_SESSION["eCartCheckoutForm_lastname"]:"") ?>|WA|<?php echo ((isset($_SESSION["eCartCheckoutForm_email"]))?$_SESSION["eCartCheckoutForm_email"]:"") ?>;
$RecipArray[$CurIndex][] = "undefined";
$TotalEmails += mysql_num_rows($<?php echo ((isset($_SESSION["eCartCheckoutForm_firstname"]))?$_SESSION["eCartCheckoutForm_firstname"]:"") ?><?php echo ((isset($_SESSION["eCartCheckoutForm_lastname"]))?$_SESSION["eCartCheckoutForm_lastname"]:"") ?>|WA|<?php echo ((isset($_SESSION["eCartCheckoutForm_email"]))?$_SESSION["eCartCheckoutForm_email"]:"") ?>);
with:
$RecipArray[$CurIndex ][] = "".((isset($_SESSION["eCartCheckoutForm_email"]))?$_SESSION["eCartCheckoutForm_email"]:"") ."";
$TotalEmails += sizeof($RecipArray[$CurIndex]);