message: Fix Null-pointer dereference in BuildXlaCompilationCache
  If ConfigProto is not used, then use the default settings which is to allow all devices.
diff: @@ -82,11 +82,13 @@ Status BuildXlaCompilationCache(DeviceBase* device, FunctionLibraryRuntime* flr,
  client_options.set_intra_op_parallelism_threads(
  device->tensorflow_cpu_worker_threads()->num_threads);
  + if (flr->config_proto()) {
  string allowed_gpus =
  flr->config_proto()->gpu_options().visible_device_list();
  TF_ASSIGN_OR_RETURN(absl::optional<std::set<int>> gpu_ids,
  ParseVisibleDeviceList(allowed_gpus));
  client_options.set_allowed_devices(gpu_ids);
  + }
  auto client = xla::ClientLibrary::GetOrCreateLocalClient(client_options);
  if (!client.ok()) {
  