Fix crash on empty database at startup.

app/src/main/java/me/zobrist/tichucounter/repository/GameRepository.kt

@@ -46,7 +46,7 @@ class GameRepository @Inject constructor(private  val gameDao: GameDao, private
     {
         return withContext(Dispatchers.IO) {
             val active = getActiveGame()
-            return@withContext roundDao.getAllForGame(active.uid)
+            return@withContext roundDao.getAllForGame(active?.uid)
         }
     }