Getting Error at top of wordpress site

Warning: join() [function.join]: Invalid arguments passed in /home/content/08/8034908/html/wp-includes/post-template.php on line 389
class=””>

This error is on this line

function post_class( $class = ”, $post_id = null ) {
// Separates classes with a single space, collates classes for post DIV
echo ‘class=”‘ . join( ‘ ‘, get_post_class( $class, $post_id ) ) . ‘”‘;
}