Fix Memcheck error found in JSON_TEST JsonReaderTest.ErrorStrings (#1…

…4164)

Fix missing null mask in string column names parsing. For parsing error, the row is made null. To write output properly, the nulls need to be passed so that they can be skipped during writing output stage in `parse_data`.
Fixes #14141

Authors:
  - Karthikeyan (https://github.com/karthikeyann)

Approvers:
  - David Wendt (https://github.com/davidwendt)
  - Elias Stehle (https://github.com/elstehle)
  - Nghia Truong (https://github.com/ttnghia)

URL: #14164

cpp/src/io/utilities/data_casting.cu

@@ -924,6 +924,9 @@ std::unique_ptr<column> parse_data(
   if (col_size == 0) { return make_empty_column(col_type); }
   auto d_null_count    = rmm::device_scalar<size_type>(null_count, stream);
   auto null_count_data = d_null_count.data();
+  if (null_mask.is_empty()) {
+    null_mask = cudf::detail::create_null_mask(col_size, mask_state::ALL_VALID, stream, mr);
+  }
 
   // Prepare iterator that returns (string_ptr, string_length)-pairs needed by type conversion
   auto str_tuples = thrust::make_transform_iterator(offset_length_begin, to_string_view_pair{data});