Fix race condition in windows::object_handle.

asio/include/asio/detail/impl/win_object_handle_service.ipp

diff --git a/asio/include/asio/detail/impl/win_object_handle_service.ipp b/asio/include/asio/detail/impl/win_object_handle_service.ipp
index f10bc4d..8afeb8c 100644
--- a/asio/include/asio/detail/impl/win_object_handle_service.ipp
+++ b/asio/include/asio/detail/impl/win_object_handle_service.ipp
@@ -429,8 +429,9 @@
       }
     }
 
+    io_service_impl& ios = impl->owner_->io_service_;
     lock.unlock();
-    impl->owner_->io_service_.post_deferred_completions(completed_ops);
+    ios.post_deferred_completions(completed_ops);
   }
 }