Fixed handling of nan for evenly_distribute_backward (#45280)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45280
Performance is the same on CPU and on CUDA is only 1-1.05x slower. This change is necessary for the future nan ops including nan(min|max|median)
Test Plan: Imported from OSS
Reviewed By: gchanan
Differential Revision: D23908796
Pulled By: heitorschueroff
fbshipit-source-id: c2b57acbe924cfa59fbd85216811f29f4af05088
