--- a/gameServer/Store.hs	Sun Jul 25 17:30:19 2010 +0200
+++ b/gameServer/Store.hs	Sun Jul 25 17:32:07 2010 +0200
@@ -77,7 +77,7 @@
 removeElem :: MStore e -> ElemIndex -> IO ()
 removeElem (MStore ref) (ElemIndex n) = do
     (busyElems, freeElems, arr) <- readIORef ref
-    IOA.writeArray arr n undefined
+    IOA.writeArray arr n (error "Store: no element")
     writeIORef ref (IntSet.delete n busyElems, IntSet.insert n freeElems, arr)