NaN values on KADID10k for IS

[snk4tr]

Describe the bug
Computation of IS for some images in KADID10k dataset causes NaN results, which is not a valid output.

To Reproduce
Steps to reproduce the behavior:

1. Checkout to feature/extend_bench
2. Run tests/resutls_benchmark.py with --dataset=kadid10k and --metrics IS
3. Print out computed metrics' values and observe torch.tensor(nan) as output for some images
4. Alternatively, finish computation of IS on all DB metrics and observe an error during computation of correlation values

Expected behavior
No NaN values are expected.

Screenshots

Additional context
Other DB metrics such as FID, MSID, KID and GS might me vulnerable.