[bug fix] Fix warning using demo recorder (#5216)

(cherry picked from commit 272899a)

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

@@ -586,14 +586,15 @@ void NotifyAgentDone(DoneReason doneReason)
             // Request the last decision with no callbacks
             // We request a decision so Python knows the Agent is done immediately
             m_Brain?.RequestDecision(m_Info, sensors);
-            ResetSensors();
 
             // We also have to write any to any DemonstationStores so that they get the "done" flag.
             foreach (var demoWriter in DemonstrationWriters)
             {
                 demoWriter.Record(m_Info, sensors);
             }
 
+            ResetSensors();
+
             if (doneReason != DoneReason.Disabled)
             {
                 // We don't want to update the reward stats when the Agent is disabled, because this will make