seems to work...

app/Main.hs

@@ -1,8 +1,10 @@
 module Main where
 
+import System.IO
 import System.Directory
 import Options.Applicative
 import Data.List
+import Control.Exception
 
 data CgiState = CgiSuccess
 instance Show CgiState where
@@ -76,3 +78,9 @@ mkIndex True d f =
    in do
         line <- trim . words . head . lines <$> readFile path
         putStrLn $ "=> " ++ path ++ " " ++ line
+
+getFirstLine :: FilePath -> IO (Maybe String)
+getFirstLine f = (Just <$> readFile f) `catch` handler
+    where
+        handler :: IOException -> IO (Maybe String)
+        handler _ = return Nothing