message: Check nullptr before we return an op.
  GetOp may return a nullptr when it fails to create a new op.
diff: @@ -68,9 +68,11 @@ TFE_Op* GetOp(TFE_Context* ctx, const char* op_or_function_name,
  }
  void ReturnOp(TFE_Op* object) {
  + if (object) {
  object->Clear();
  thread_local_eager_operation.reset(object);
  }
  +}
  TF_Status* ReleaseThreadLocalStatus() {
  if (thread_local_tf_status == nullptr) {
  