[PyTorch] Don't do extra numel() check in TensorImpl::data() (#98090)
`is_empty()` checks `numel() == 0`, but we don't need to access `numel_` at all (or the policy that `numel()` checks) in our happy path -- we just need the data pointer from `storage_`. Let's do the check we need to do using only the data we strictly need, rather than adding instructions loading other pieces of data.
Differential Revision: [D44586464](https://our.internmc.facebook.com/intern/diff/D44586464/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/98090
Approved by: https://github.com/Skylion007
