Javascript error

I get this error in firebug:

TypeError: e is undefined
e.setAttribute(‘unselectable’,on);
I traced it to this snippet:

<script id=”wpcp_css_disable_selection” type=”text/javascript”>
var e = document.getElementsByTagName(‘body’)[0];
e.setAttribute(‘unselectable’,on);
</script>

Plugin works properly though

https://ww.wp.xz.cn/plugins/wp-content-copy-protector/