Fatal Error – Buddybar logo changer

I tried to upload the Buddy Bar logo changer plugin in order to add my own logo to the website but when I login into word press to change my website the following message comes up with a white screen:

*Fatal error*: Call to undefined function is_site_admin() in */homepages/32/d368129788/htdocs/Capitaldms/wp-content/plugins/cd-buddybar-logo-changer/cd-bblc.php* on line *36*

Can anyone help as my website is not finished and I am unable to edit it or prevent the public from viewing it!

Thanks