Fix error of 'Runner' object has no attribute 'log_buffer' (#259)

* fix 'Runner' object has no attribute 'log_buffer'

* update

* add train

mmengine/hooks/optimizer_hook.py

@@ -92,8 +92,8 @@ class OptimizerHook(Hook):
             grad_norm = self.clip_grads(runner.model.parameters())
             if grad_norm is not None:
                 # Add grad norm to the logger
-                runner.log_buffer.update({'grad_norm': float(grad_norm)},
-                                         runner.outputs['num_samples'])
+                runner.message_hub.update_scalar('train/grad_norm',
+                                                 float(grad_norm))
         runner.optimizer.step()
 
     def detect_anomalous_parameters(self, loss: torch.Tensor, runner) -> None: