Fix crash on map load

src/main.rs

@@ -146,10 +146,12 @@ fn draw(game: &mut GOL) {
     game.write(&'X');
     for col in 1..size.0 {
         for row in 1..size.1 {
-            let cell: char =
-                game.map[(row + game.player.pos.x) as usize][(col + game.player.pos.y) as usize];
-            game.write(&cursor::Goto(row, col));
-            game.write(&cell);
+            if let Some(r) = game.map.clone().get_mut((row + game.player.pos.x) as usize) {
+                if let Some(cell) = r.get_mut((col + game.player.pos.y) as usize) {
+                    game.write(&cursor::Goto(row, col));
+                    game.write(&cell);
+                }
+            }
         }
     }
     game.flush();