Fix a leftover _has_nulls change from Nullate (#10211)

There was one missed change from template param has_nulls to member Nullate _has_nulls. It worked because has_nulls resolved to pointer to the function `has_nulls(table_view)` which is always true and didn't break at runtime because the subsequent is_null has a built in nullmask check.

Authors:
  - Devavret Makkar (https://github.com/devavret)

Approvers:
  - David Wendt (https://github.com/davidwendt)
  - Ram (Ramakrishna Prabhu) (https://github.com/rgsl888prabhu)
  - Mike Wilson (https://github.com/hyperbolic2346)

URL: #10211

cpp/include/cudf/table/row_operators.cuh

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2021, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2022, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -233,7 +233,7 @@ class row_equality_comparator {
   row_equality_comparator(Nullate has_nulls,
                           table_device_view lhs,
                           table_device_view rhs,
-                          null_equality nulls_are_equal = true)
+                          null_equality nulls_are_equal = null_equality::EQUAL)
     : lhs{lhs}, rhs{rhs}, nulls{has_nulls}, nulls_are_equal{nulls_are_equal}
   {
     CUDF_EXPECTS(lhs.num_columns() == rhs.num_columns(), "Mismatched number of columns.");
@@ -465,7 +465,7 @@ class element_hasher_with_seed {
   template <typename T, CUDF_ENABLE_IF(column_device_view::has_element_accessor<T>())>
   __device__ hash_value_type operator()(column_device_view col, size_type row_index) const
   {
-    if (has_nulls && col.is_null(row_index)) { return _null_hash; }
+    if (_has_nulls && col.is_null(row_index)) { return _null_hash; }
     return hash_function<T>{_seed}(col.element<T>(row_index));
   }