Pretty new to WPP, so apologies if this is known (either to be good or bad), but hoping it might help some folks.
I'm using WPP on a site that includes BuddyPress. BuddyPress is a good example of a plugin that generated pages that don't have post ids associated with them, per se.
I've found this to cause JS errors on such pages, as the basic wpp_update call is looking for an $id param, which equates to null. I altered wordpress-popular-posts.php to first check to see if it has an id before firing the wpp_update call:
(note the if($id) )
... and this seems to have resolved the issue.
If there's a better way, or this is actually straight-up bad, please let me know!