[FX] Fix NoneType annotation in generated code (#50777)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/50777
Test Plan: Imported from OSS
Reviewed By: Chillee
Differential Revision: D25966026
Pulled By: jamesr66a
fbshipit-source-id: 8e36521eee03eade7e1b602e801229c085b03488
