Fix ASAN div by zero error in rotated GenerateProposals op (#15415)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15415
Was introduced in D13429770
Reviewed By: SuperIRabbit
Differential Revision: D13524114
fbshipit-source-id: a890eb3b97c24952c361155d1432a801499f4ddd
