Fix bug not adding last positioned room to list

src/Dodge/Tree/Compose.hs

@@ -11,6 +11,7 @@ module Dodge.Tree.Compose
     ) where
 import Dodge.Tree.Compose.Data
 import Dodge.Tree.Polymorphic
+import Dodge.Base
 import Data.Tree
 
 expandTree :: CompTree a -> Tree a
@@ -24,7 +25,8 @@ expandTree (Node root extChildren) = case root of
             $ map (:[]) extChildren ++ repeat []
 
 overwriteLabel :: Int -> (a -> ComposingNode a) -> SubCompTree a -> [SubCompTree a] -> SubCompTree a
-overwriteLabel i f t ts = head $ updateSingleNode islabel update t
+overwriteLabel i f t ts = errorHead ("tried to overwriteLabel " ++ show i)
+    $ updateSingleNode islabel update t
   where
     islabel (UseLabel j _) | i == j = True
     islabel _ = False