Our team is not experiencing this issue. The variable you are referring to, is initialized during the first function call, every time the plugin starts.
The function which initializes constants must be called before buddypress is initialized. So in short, its theoretically impossible for the variable not to be set in buddypress.
Your best bet is to install the latest version of the plugin and remove any custom files. Alternatively, you could have one of our developers check out your installation as “product support”. Currently the cost of this service is $15/hr
BePro Software Team