Fatal error: Call to undefined function is_site_admin() in /home/blogong8/public_html/aboutsingapore

Hello Support,

I hit this error when trying to activate the Ultimate Translate plugin.

Fatal error: Call to undefined function is_site_admin() in /home/blogong8/public_html/aboutsingaporecasino.com/wp-content/plugins/1280374391627/update-notifications.php on line 417

I am using version 1.0.1.

My Wordpress version is a normal regular single user Wordpress.

My Wordpress version is 2.8.4.

What should I do?