[BUG] cudf::hash_join throws exception when computing inner join size of empty build table

[jlowe]

Describe the bug
cudf::hash_join will throw an exception like the following when constructing the instance from a table with zero rows and subsequently calling the inner_join_size() method.

Steps/Code to reproduce bug
Apply the following patch and run the join tests

+TEST_F(JoinTest, HashJoinEmpty)
+{
+  CVector cols1;
+  cols1.emplace_back(column_wrapper<int32_t>{}.release());
+
+  Table t1(std::move(cols1));
+
+  cudf::hash_join hash_join(t1, cudf::null_equality::EQUAL);
+
+  {
+    CVector cols0;
+    cols0.emplace_back(column_wrapper<int32_t>{{4, 1, 2, 0, 3}}.release());
+
+    Table t0(std::move(cols0));
+
+    auto output_size                         = hash_join.inner_join_size(t0);
+    std::optional<std::size_t> optional_size = output_size;
+
+    std::size_t const size_gold = 0;
+    EXPECT_EQ(output_size, size_gold);
+
+    auto result = hash_join.inner_join(t0, cudf::null_equality::EQUAL, optional_size);
+    auto result_table =
+      cudf::table_view({cudf::column_view{cudf::data_type{cudf::type_id::INT32},
+                                          static_cast<cudf::size_type>(result.first->size()),
+                                          result.first->data()},
+                        cudf::column_view{cudf::data_type{cudf::type_id::INT32},
+                                          static_cast<cudf::size_type>(result.second->size()),
+                                          result.second->data()}});
+    auto result_sort_order = cudf::sorted_order(result_table);
+    auto sorted_result     = cudf::gather(result_table, *result_sort_order);
+
+    column_wrapper<int32_t> col_gold_0{};
+    column_wrapper<int32_t> col_gold_1{};
+
+    CVector cols_gold;
+    cols_gold.push_back(col_gold_0.release());
+    cols_gold.push_back(col_gold_1.release());
+
+    Table gold(std::move(cols_gold));
+    auto gold_sort_order = cudf::sorted_order(gold.view());
+    auto sorted_gold     = cudf::gather(gold.view(), *gold_sort_order);
+
+    CUDF_TEST_EXPECT_TABLES_EQUIVALENT(*sorted_gold, *sorted_result);
+  }
+}
+

Expected behavior
cudf::hash_join should return 0 when calling inner_join_size() when the table passed on instance construction was empty. Similarly a subsequent inner_join call should return empty gather maps.

[PointKernel]

This issue is similar to #9044.

I will make a PR to fix both of them.