Fix torch.sparse.sum parsing of dim. (#16517)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/16501.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16517
Differential Revision: D13865322
Pulled By: gchanan
fbshipit-source-id: fa0ac37a9e7b8f19a5bdf75e5771128e48c41612
