Fix step used to log SAC summary

fixes hill-a#1007

stable_baselines/sac/sac.py

@@ -314,6 +314,7 @@ def setup_model(self):
                 self.summary = tf.summary.merge_all()
 
     def _train_step(self, step, writer, learning_rate):
+        del step
         # Sample a batch from the replay buffer
         batch = self.replay_buffer.sample(self.batch_size, env=self._vec_normalize_env)
         batch_obs, batch_actions, batch_rewards, batch_next_obs, batch_dones = batch
@@ -336,7 +337,7 @@ def _train_step(self, step, writer, learning_rate):
         if writer is not None:
             out = self.sess.run([self.summary] + self.step_ops, feed_dict)
             summary = out.pop(0)
-            writer.add_summary(summary, step)
+            writer.add_summary(summary, self.num_timesteps)
         else:
             out = self.sess.run(self.step_ops, feed_dict)