Fatel error after disabled bbPress

Thank you for the great plugin!

I have used Private BP Pages with BuddyPress and bbPres.
I disabled bbPress since no one use it. After I disabled bbPress, my page showed the following error message.
Fatal error: Call to undefined function bbp_is_single_forum() in C:\xampp\htdocs\bomop\wp-content\plugins\private-bp-pages\private-bp-pages.php on line 8

The app version I have used are:
WordPress 3.9.2
BuddyPress 2.0.2
bbPress 2.5.4
Private BP Pages 1.3

Thank you for any help you can provide.

https://wordpress.org/plugins/private-bp-pages/