Make the demoRecorder write the experience on reset (#3463)

* Make the demoRecorder write the experience on reset

* do nothing if demostore is null

* Calling reset data if the action is null

com.unity.ml-agents/Runtime/Agent.cs

             // We request a decision so Python knows the Agent is done immediately
             m_Brain?.RequestDecision(m_Info, sensors);
 
+            if (m_Recorder != null && m_Recorder.record && Application.isEditor)
+            {
+                m_Recorder.WriteExperience(m_Info, sensors);
+            }
+
             UpdateRewardStats();
 
             // The Agent is done, so we give it a new episode Id
             if ((m_RequestAction) && (m_Brain != null))
             {
                 m_RequestAction = false;
-                if (m_Action.vectorActions != null)
-                {
-                    AgentAction(m_Action.vectorActions);
-                }
+                AgentAction(m_Action.vectorActions);
             }
         }
 
+            if (m_Action.vectorActions == null){
+                ResetData();
+            }
         }
     }
 }

com.unity.ml-agents/Runtime/DemonstrationRecorder.cs

         /// </summary>
         public void WriteExperience(AgentInfo info, List<ISensor> sensors)
         {
-            m_DemoStore.Record(info, sensors);
+            m_DemoStore?.Record(info, sensors);
         }
 
         public void Close()