add support for None in assert_close (#67795)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67795
Closes #61035.
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D32532207
Pulled By: mruberry
fbshipit-source-id: 6a2b4245e0effce4ddea7d89eca63e3b163951a7
