fix(NetworkServer): Call NetworkClient.InvokeUnSpawnHandler from UnSp…

…awnInternal

- Fixes #3962
There may be a custom unspawn handler for the prefab and NetworkClient::OnHostClientObjectDestroy doesn't invoke it and can't because it's already out of spawned dictionary.

Assets/Mirror/Core/NetworkServer.cs

@@ -1720,6 +1720,9 @@ static void UnSpawnInternal(GameObject obj, bool resetState)
             // in host mode, call OnStopClient/OnStopLocalPlayer manually
             if (NetworkClient.active && activeHost)
             {
+                // custom unspawn handler for this prefab (for prefab pools etc.)
+                NetworkClient.InvokeUnSpawnHandler(identity.assetId, identity.gameObject);
+
                 if (identity.isLocalPlayer)
                     identity.OnStopLocalPlayer();