bugfix: allow superfluous "/" in paths

esp. a trailing / as in bahnhof.name/MH/ should not lead to ??.

app/Main.hs

@@ -107,7 +107,7 @@ app :: AppData -> Application
 app AppData{..} request respond = mkAnswer >>= (respond . toResponse)
   where
     mkAnswer :: IO Answer
-    mkAnswer = case pathInfo request of
+    mkAnswer = case filter (/= mempty) (pathInfo request) of
       [] -> pure helptext
       ["favicon.ico"] -> pure Notfound
       ["cache"] -> do