Network Spawned object and Sync var hook possible race condition.

[JesusLuvsYooh]

Describe the bug
A network spawned object as sync var, triggers a hook call when changed, but is not found or ready to use in hook code.
Start player host, spawn network object, have a sync var hook set this sync var object in player code.
Join via a second player, you can see the hooks called, but it is not usable in hooks code.

• This only happens if object is network spawned (not set in scene), and with a late joining player. -

[SyncVar(hook = nameof(OnPickupChangedHook))]
public NetworkIdentity pickedUpNetworkObject;

void OnPickupChangedHook(NetworkIdentity _old, NetworkIdentity _new)
{
  print("OnPickupChangedHook 1");

  if (pickedUpNetworkObject)
  {
    print("OnPickupChangedHook 2");
    PickupResult();
  }
  else
  {
  print("OnPickupChangedHook 3");
    DropResult();
  }
}

print("OnPickupChangedHook 1"); is called, but print("OnPickupChangedHook 2"); is not.

Adding a 1 frame delay works, example:

 [SyncVar(hook = nameof(OnPickupChangedHook))]
        public NetworkIdentity pickedUpNetworkObject;

        void OnPickupChangedHook(NetworkIdentity _old, NetworkIdentity _new)
        {
            StartCoroutine(WaitForResult());
        }

        private IEnumerator WaitForResult()
        {
            // we use a delay, as network spawned objects may not be spawned in and ready, hooks get called very early
            yield return new WaitForEndOfFrame();
            print("OnPickupChangedHook 1" + pickedUpNetworkObject);
            if (pickedUpNetworkObject)
            {
                print("OnPickupChangedHook 2" + pickedUpNetworkObject);
                PickupResult();
            }
            else
            {
                print("OnPickupChangedHook 3");
                DropResult();
            }
        }

[MrGadget1024]

Duplicate of #3097