Put error back and fix timetravel

Author: EmandM

com.unity.netcode.gameobjects/Runtime/Core/NetworkObject.cs

@@ -2632,9 +2632,7 @@ private List<NetworkBehaviour> BuildChildBehavioursList()
         {
             if (NetworkManagerOwner == null)
             {
-#if TEST_NO_SINGLETON
                 Debug.LogError("NetworkManagerOwner should be set! Setting owner to NetworkManager.Singleton");
-#endif
                 NetworkManagerOwner = NetworkManager.Singleton;
             }
 

com.unity.netcode.gameobjects/Tests/Runtime/TestHelpers/NetcodeIntegrationTest.cs

@@ -2561,10 +2561,13 @@ public static void SimulateOneFrame()
                         var method = obj.GetType().GetMethod(methodName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
                         method?.Invoke(obj, new object[] { });
 
-                        foreach (var behaviour in obj.ChildNetworkBehaviours)
+                        if (obj.IsSpawned)
                         {
-                            var behaviourMethod = behaviour.GetType().GetMethod(methodName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
-                            behaviourMethod?.Invoke(behaviour, new object[] { });
+                            foreach (var behaviour in obj.ChildNetworkBehaviours)
+                            {
+                                var behaviourMethod = behaviour.GetType().GetMethod(methodName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
+                                behaviourMethod?.Invoke(behaviour, new object[] { });
+                            }
                         }
                     }
                 }