[torch] handle embedding bag with empty bag (#57446)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57446
GPU EmbeddingBag is handling L == 0 . Matching CPU version.
Test Plan: buck test //deeplearning/fbgemm/fbgemm_gpu:split_table_batched_embeddings_test -- test_forward
Reviewed By: jiyuanzFB
Differential Revision: D28145090
fbshipit-source-id: d91d0050ddd5636293a8965d3eece02633918f4c
