fix build breakage of //sigrid/... (#36206)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36206
nothing wrong with the code, adding appropriate casts
to keep the compiler happy
Test Plan:
build //sigrid/...
tests in the same directory
buck test //glow/glow/tests/fakelowp/...
Reviewed By: jspark1105
Differential Revision: D20911279
fbshipit-source-id: 086ef028006a53048e1cfbe9dbc6c4bdd18fb259
