HELP: Comment Error

Hi,

I upload a new theme that I purchased and it now says the following when you go to post a comment, as an admin I can post a comment but guests cannot:

Blog

<input type=”text” name=”author” id=”author” value=”
Fatal error: Call to undefined function esc_attr() in /home/amod/public_html/edmontonweddingplanner/wp-content/themes/tofurious-22/comments.php on line 58

Any help would be much appreciated. The line it is refering to (#58 in the comments.php file reads:

<p><input type=”text” name=”author” id=”author” value=”<?php echo esc_attr($comment_author); ?>” size=”22″ tabindex=”1″ <?php if ($req) echo “aria-required=’true'”; ?> />