Fix MAGMA qr for empty batched inputs (#56257)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56257
CPU and cuSOLVER path were fixed with refactoring of
`_linalg_qr_helper_default`.
Resolves https://github.com/pytorch/pytorch/issues/50576
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D27960157
Pulled By: mruberry
fbshipit-source-id: f923f3067a35e65218889e64c6a886364c3d1759
