Fix for App crash on enemy controller assigned

void UEnemySubsystem::RequestEnemy()
{
    if(TotalEnemiesToSpawnThisRound-- == 0)
    {
        GetWorld()->GetTimerManager().ClearTimer(EnemySpawnTimerHandle);
        EnemySpawnTimerHandle.Invalidate();
        return;
    }

    // Clear and invalidate the timer if the remaining enemies to spawn is 0
    const auto SpawnPoint = GetRandomEnemySpawnPoint();

    const auto Controller = mFreeControllers.Pop(true); // take out a free controller
    Controller->SpawnPawn(SpawnPoint);  // spawn the pawn
    mAllocatedController.Add(Controller);   // add it to the allocated controller
}