Unhandled Error!

  <div class="post underline gBorder">
        <div class="row">
            <div class="span6point5"></div>
            <div class="span16 offsetpoint5">
                <h1><a href="<?php echo root_url('blog/post/'.$post->url_title); ?>"><?php echo h($post->title); ?></a></h1>
            </div>
        </div>
        <div class="row">
            <div class="span6point5 align-right">
                <p class="date"><strong><?php echo $post->published_date->format('%e %B %Y'); ?></strong></p>
                <p class="categories">
					<? foreach($post->categories as $i=>$category): ?><a href="<?= root_url('blog/category/'.$category->url_name); ?>"><?= $category->name; ?></a><?= $i == $post->categories->count - 1 ? '' : ', '; ?><?php endforeach; ?>
                </p>