Do not return unitialized qschame from getQSchemeAndQParamVector (#49391)
Summary:
Assign it by default to `kPerTensorAffine`
Fixes regressions accidentally discovered by https://app.circleci.com/pipelines/github/pytorch/pytorch/250370/workflows/6f38ae43-a9a5-43f3-8c1f-0f911df69d75/jobs/9589799
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49391
Reviewed By: ngimel
Differential Revision: D25554180
Pulled By: malfet
fbshipit-source-id: f42a45e9d6743c665c62d057197d009f1542226e
