array_merge的問題

今天用了wyo版型，發現安裝完後會有這樣的錯誤碼：

warning: array_merge() [function.array-merge]: Argument #1 is not an array in /sites/all/themes/wyo/template.php on line 318.


然後打開該檔案，line318內容如下：
$output .= '


整段

<?php

function wyo_primary_links($links) {

$num_links = count($links);
$i = 1;

$output = '';
foreach ($links as $index => $link) {

$class = 'plink';

// Add first, last and active classes to the list of links to help out themers.
if ($i == 1) {
$class .= ' first';
}
if ($i == $num_links) {
$class .= ' last';
}

$plink_div_class = 'plink_div';
if (($link['href'] == $_GET['q']) || ($path == '' && drupal_is_front_page())) {
$plink_div_class = $plink_div_class .' active';
}

//以下開始是 line 318
$output .= '

';

$i++;
}
$output .= '';
return $output;
}
?>

不知問題出在哪邊？