[PyTorch] Avoid reading file from stream for 0 byte Tensor storage (#67787)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67787
First noticed in https://fb.workplace.com/groups/pytorch.edge.team/posts/952737705280969/ - basically one of the speech models has ~400 0 byte tensor files, so we're basically paying the cost of looking it up in the archive and reading nothing from it.
Turns out that there's a fairly simple fix to avoid reading a 0 byte tensor. Once we notice that it's 0 bytes, just use the default `DataPtr` instead to initializing it with 0 bytes read in from the input file stream.
ghstack-source-id: 142025211
Test Plan: CI and manually ran a couple production mobile models with bundled inputs. CI Will run all prod. mobile mobiles with bundled inputs.
Reviewed By: swolchok
Differential Revision: D32054983
fbshipit-source-id: 919b0cdbc44bccb8f6cfe0da10ff5474af37fd99
