Error message new site Domainmapping

i got this errormessage by trying to register a new site for a user whit the Domainmappignplugin:
Fatal error: Call to undefined function bp_blogs_subdomain_base() in /var/www/web709/html/wp-content/themes/OneCommunity/registration/register.php on line 221

The row nr. 221 in the register.php is the following:
http:// <input type="text" name="signup_blog_url" id="signup_blog_url" value="<?php bp_signup_blog_url_value(); ?>" /> .<?php bp_blogs_subdomain_base(); ?>

Someone an idea to start an effective debugging?

Thanks for all inputs!