Error instead of assertion failure for div by sparse (#30260)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30260
fixes: https://github.com/pytorch/pytorch/issues/30044
Without this PR,
```
>>> torch.tensor(1.) / torch.tensor(1.).to_sparse()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: r.is_sparse() INTERNAL ASSERT FAILED at /Users/distiller/project/conda/conda-bld/pytorch_1570710797334/work/aten/src/ATen/native/sparse/SparseTensorMath.cpp:168, please report a bug to PyTorch.
```
Test Plan:
Ran the same code with this change:
```
In [1]: import torch
In [2]: torch.tensor(1).to_sparse() / torch.tensor(1).to_sparse()
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-2-7177f54f30bb> in <module>
----> 1 torch.tensor(1).to_sparse() / torch.tensor(1).to_sparse()
RuntimeError: Unsupported tensor layout
```
Differential Revision: D18657387
Pulled By: nairbv
fbshipit-source-id: cd23570d46f5b26fd84049e5e63b61b19835603d
