Add System.Directory library, allow for testing file existence

package.yaml

@@ -45,6 +45,7 @@ dependencies:
 - foldl
 - linear
 - aeson
+- directory
 
 library:
   source-dirs: src

src/LoadConfig.hs

@@ -10,6 +10,8 @@ import qualified GHC.Int
 import qualified SDL
 import SDL.Internal.Numbered as SDL.Internal.Numbered
 
+import System.Directory
+
 data Configuration = Configuration
   { windowxsize :: Int,
     windowysize :: Int
@@ -133,6 +135,9 @@ instance FromJSON KeyConfig where
 
 loadKeyConfig :: IO KeyConfigSDL
 loadKeyConfig = do
+    fExists <- doesFileExist "keys.json"
+    if fExists
+    then do
         mayConfig <- decodeFileStrict "keys.json"
         print mayConfig
         case mayConfig of
@@ -160,6 +165,7 @@ loadKeyConfig = do
             putStrLn "invalid keys.json, loading default config"
             -- This is duplicated but not sure how to reduce
             return defaultKeyConfigSDL
+    else return defaultKeyConfigSDL
 
 getSdlScancode :: Int -> SDL.Scancode
 getSdlScancode x = SDL.Internal.Numbered.fromNumber (fromIntegral x) :: SDL.Scancode