pull empty() out of use_c10_dispatcher: full (#43572)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/43572
Test Plan: Imported from OSS
Reviewed By: smessmer
Differential Revision: D23326019
Pulled By: bhosmer
fbshipit-source-id: 10a4d7ffe33b4be4ae45396725456c6097ce1757
