Fix empty rank broken test (#2746)

Summary:
Pull Request resolved: #2746

as per title.

Reviewed By: sarckk

Differential Revision: D69684770

fbshipit-source-id: 190081b2b91cc05c85f309202691927cf416f352

Author: dstaay-fb

torchrec/distributed/tests/test_model_parallel_hierarchical.py

@@ -232,6 +232,7 @@ def test_sharding_nccl_twcw(
     def test_sharding_empty_rank(
         self, sharding_type: str, variable_batch_per_feature: bool
     ) -> None:
+        self._build_tables_and_groups()
         table = self.tables[0]
         embedding_groups = {"group_0": table.feature_names}
         self._run_multi_process_test(