Advanced Theme Switcher provokes issue

Hi,
i got this error message after installing the Advanced Theme Switcher Plugin:

Fatal error: Call to a member function get() on a non-object in /var/www/web38/html/helpingninja.com/wp-includes/query.php on line 27

Can you check this issue in the plugin?
I work whit Wordpress 3.7.1, Buddypress and Multisite.

Thanks!