So I have removed sigmoid from the final layer. These are the values of outputs, loss, gradient:
tensor([[42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,
         39.2434, 42.2288],
        [42.0968, 36.8111, 41.2566, 41.8263, 42.0318, 43.3060, 40.5994, 41.5220,

LOSS:
tensor(3.8067, device='cuda:0', grad_fn=<NllLossBackward>)
tensor(3.4348, device='cuda:0', grad_fn=<NllLossBackward>)
tensor(2.8786, device='cuda:0', grad_fn=<NllLossBackward>)
tensor(2.9722, device='cuda:0', grad_fn=<NllLossBackward>)

Gradient:
tensor([[ 0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00],
        [ 0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,
          0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,  0.0000e+00,