Minor fix in package exporter (#90306)
Summary:
As title.
Saw this while working on another diff.
`storage` won't be defined in the `else` case. But this causes pyre to freak out.
Test Plan: Unit tests.
Differential Revision: D41751229
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90306
Approved by: https://github.com/PaliC
