Undefined constants

Hello, I love your plugin. I have recently found this message alongside it on my site.

Notice: Use of undefined constant tab – assumed ‘tab’ in /var/sites/t/tomofteignmouth.co.uk/public_html/wp-content/plugins/gplus-comments/includes/templates/container.php on line 62

on my site, for example..

http://www.tomofteignmouth.co.uk/socks-sandals-the-campaign-begins/

any assistance most welcome. I hope all is well,

Tom

https://ww.wp.xz.cn/plugins/gplus-comments/