Error: Missing argument, line 45!?

I cant get this plugin to work, I keep getting this error..

Warning: Missing argument 2 for Bhu_C2S_subscription_add() in …/public_html/wp-content/plugins/bhu-c2s/Bhu_C2S.php on line 45

Any ideas? Line 45 begins with this:

function Bhu_C2S_subscription_add( $cid, $comment ) {
  $cid = (int) $cid;

  if ( !is_object($comment) )
    $comment = get_comment($cid);

  if ( $comment->comment_karma == 0 ) {
   $subscribe = get_comment_meta($cid, 'mailchimp_subscribe', true);
if ( $subscribe == 'on' ) {
update_comment_meta($cid, 'mailchimp_subscribe', 'off');

/////////////////////////////////////
///////MailChimp////////////////////
///////////////////////////////////
  $apikey   = get_option('shamboapikey');
$listid   =  get_option('shambolistid');
$endpoint   = 'https://'.get_option('shamboendpoint').'.api.mailchimp.com/1.3/?output=php';

$request   = array(
  'apikey' => $apikey,
  'id' => $listid,
  'email_address' => strtolower( $comment->comment_author_email ),
  'double_optin' => true,
  'merge_vars' => array(
    ' <merge tag for name> ' => $comment->comment_author,
    'OPTIN_IP' => $comment->comment_author_IP,
  )
);
$result = wp_remote_post(
  $endpoint.'&method=listSubscribe',
  array( 'body' => json_encode($request) )
);
/////////////////////////////////////
///////MailChimp  Ended////////////////////
///////////////////////////////////

}

Best regards,
SNURK