Breaks wp-admin – error in php code

Because of a bug in code, wp-admin showed a blank screen. Viewing HTML Source of /wp-admin shows it stops at this line:
<script type="text/javascript">var wpurl =

After digging, it looks like it is an error in the file /wp-content/plugins/cart66-lite/models/Cart66.php, line 307:

public function registerBasicScripts() {
    ?><script type="text/javascript">var wpurl = '<?php echo esc_js( home_url('/') ); ?>';</script><?php
  }