fix bug (#51222) (#51527)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51527
Fix bug in scatter_add symbolic
Test Plan: Imported from OSS
Reviewed By: pbelevich
Differential Revision: D26203119
Pulled By: SplitInfinity
fbshipit-source-id: e61f024e2daa7bc396fb264b8823a72ebf94ccdb
