Fix space leak when assigning targeted creature

src/Dodge/Creature/Impulse/UseItem.hs

@@ -8,7 +8,7 @@ import Dodge.Data
 
 import qualified Data.IntMap.Strict as IM
 import Control.Lens
---import Data.Maybe
+import Data.Maybe
 
 useItem :: Int -> World -> World
 useItem cid w = itemEffect cr it w
@@ -17,9 +17,10 @@ useItem cid w = itemEffect cr it w
     it = _crInv cr IM.! _crInvSel cr
 
 tryUseItem :: Creature -> World -> World
-tryUseItem cr' w = case w ^? creatures . ix (_crID cr') of
-    Just cr -> itemEffect cr (_crInv cr IM.! _crInvSel cr) w
-    Nothing -> w
+tryUseItem cr' w = fromMaybe w $ do
+    cr <- w ^? creatures . ix (_crID cr')
+    it <- cr ^? crInv . ix (_crInvSel cr)
+    return $ itemEffect cr it w
 
 itemEffect :: Creature -> Item -> World -> World
 itemEffect cr it w = case it ^? itUse of