Unhandled Error!

Trying to get property of non-object

Document	product_partial
Document type	CMS partial
Line	3
Exception class	Cms_ExecutionException

Code Highlight

<div class="span4 gutter">
				<div class="box main_image_wrap">
				<? if ($product->on_sale): ?>
					<div class="sale_banner"><img src="<?= resource_url('/images/sale.png') ?>"></div>
				<?php elseif($product->garbee_preorder): ?>
					<div class="sale_banner"><img src="<?= resource_url('/images/preorder.png') ?>"></div>
 
				<? endif; ?>
				<script>
				$(document).ready( function() {
					$('.carousel').carousel({
						interval: 5000
					})

#	Document	Type
2	product_partial	CMS partial
1	Product	CMS page