Improve item location code, including some error detection

src/Dodge/Inventory/Location.hs

@@ -1,4 +1,9 @@
 module Dodge.Inventory.Location
+    (updateRootItemID
+    , crUpdateItemLocations
+    , setInvPosFromSS
+    , tryGetRootItemInvID
+    )
     where
 import Dodge.Base.You
 import Dodge.Data.SelectionList
@@ -12,7 +17,9 @@ import Control.Applicative
 
 tryGetRootItemInvID :: Int -> Creature -> Maybe Int
 tryGetRootItemInvID i cr = do
-    let adj = invAdj (_crInv cr)
+    let adj = case invAdj' (_crInv cr) of
+            Left str -> error $ "tryToGetRootItemInvID: "++ str
+            Right x -> x
     thetree <- adj ^? ix i -- to check that the index does point to SOME item in the inventory
     thetree ^? _1 . _Just . _1 <|> Just i