Encountering the same issue/error dealing with emptying spam and even comment replies. Commenting out line 33 of Util_AttachToActions.php as suggested resolved the issue on my install. I see this will be resolved in an upcoming update, but wanted to share my experience with the temporary fix.
HP Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class W3TC\Util_AttachToActions does not have a method “on_comment_status” in ../wp-includes/class-wp-hook.php:308