If you are getting this error, until someone posts a better fix, you can just comment out lines 693 and 694. Crafting will no longer be counted, but the plugin will work at least.

void OnItemCraftFinished(ItemCraftTask itemCraftTask, Item item)
{
// WPBPlayer wpbPlayer = GetWPBPlayer(itemCraftTask.owner);
// if (wpbPlayer != null) wpbPlayer.Stats.CraftedItems++;
}


Add the "//"s before the 2 lines like in the above.