Make sure cat list is an array. Props: Peter Westwood

git-svn-id: http://svn.automattic.com/wordpress/trunk@2683 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions-post.php

@@ -229,6 +229,9 @@ function wp_get_post_cats($blogid = '1', $post_ID = 0) {
 
 	$result = $wpdb->get_col($sql);
 
+	if ( !$result )
+		$result = array();
+
 	return array_unique($result);
 }