Tighten error checking in ConcreteModuleType (#37813)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37813
This condition should never fire.
Test Plan: Imported from OSS
Reviewed By: jamesr66a
Differential Revision: D21398021
Pulled By: suo
fbshipit-source-id: 7f2213a020071b8eab80ef40ac6a9de669722548
