Warning: Invalid argument supplied for foreach()

plugin version 1.4

error show on front page

Warning: Invalid argument supplied for foreach() in /domain.com/wp-content/plugins/facebook-import-comments/classes/FacebookCommentImporter.php on line 189

my code

line 188    private function importComments($comments, $parentCommentId = NULL) {
line 189        foreach ($comments as $num => $comment) {
line 190            $this->importComment($comment, $parentCommentId);
line 192        }
    }