Don't run initEvent when loading the game

Rather than having a single sentWelcome boolean, avoid running the
initEvent entirely when loading an already-initialized game. Among other
things, this stops us from re-generating a level and then merging it
with the existing one when the game is loaded (oops).

src/Xanthous/Game/Lenses.hs

@@ -56,7 +56,6 @@ initialStateFromSeed seed =
       _debugState = DebugState
         { _allRevealed = False
         }
-      _sentWelcome = False
   in GameState {..}