Zero slice bug (#20914)
Summary:
Bug reported internally at FB:
```python
>>> t=torch.from_numpy(np.empty((0,4)))
>>> t[:,1::2]*=1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: Trying to resize storage that is not resizable at ../aten/src/TH/THStorageFunctions.cpp:76
```
This happens because the storage offset of `t[:, 1::2]` is 1, and it has 0 elements. We can fix this by avoiding resizing the storage for no-element arrays.
(We could *also* have avoided it by not modifying the storage index in this case, but I felt this way was more semantically correct -- in general, we should not be assuming it's okay to do anything to the storage when it has zero elements).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20914
Differential Revision: D15497860
Pulled By: umanwizard
fbshipit-source-id: 6af61d73a05edfc5c07ce8be9e530f15bf72e6a9
