remove setStorage with null StorageImpl support. (#33735)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33735
This apparently used to create a new storage, but I couldn't find anywhere in the code where this actually happens.
Changing it to an assert to see what happens.
Test Plan: Imported from OSS
Differential Revision: D20084029
Pulled By: gchanan
fbshipit-source-id: e9c4db115a25fc2e17a3b166c1ff5a0e6b56d690
