Fix `torch.median` crash on empty tensor (#61698)
Summary:
`torch.tensor([]).median()` returns `nan`, which mimics the behavior of `np.median`
Add test to `TestReductions.test_median_corner_cases`
Fixes https://github.com/pytorch/pytorch/issues/61656
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61698
Reviewed By: heitorschueroff
Differential Revision: D29706912
Pulled By: malfet
fbshipit-source-id: ea5f58327fbff371f3fb8786b269430c7a10d05f
