ArgumentNullException in NetworkTransform when destroying a scene with disabled NetworkTransform GameObjects

[zachstronaut]

When developing in the Editor we might have a scene additively loaded, but testing the "real" game workflow might mean we immediately destroy that additive scene and load some other scene when we press the Play button in the Editor.

Netcode 1.6.0

If I do that and destroy an additive scene that had disabled GameObjects which had NetworkTransform components I get the following error:

ArgumentNullException: String reference not set to an instance of a String.
Parameter name: s
System.Text.Encoding.GetBytes (System.String s) (at <787acc3c9a4c471ba7d971300105af24>:0)
Unity.Netcode.CustomMessagingManager.UnregisterNamedMessageHandler (System.String name) (at ./Packages/[email protected]/Runtime/Messaging/CustomMessageManager.cs:218)
Unity.Netcode.Components.NetworkTransform.OnNetworkDespawn () (at ./Packages/[email protected]/Components/NetworkTransform.cs:2494)
Unity.Netcode.NetworkBehaviour.InternalOnNetworkDespawn () (at ./Packages/[email protected]/Runtime/Core/NetworkBehaviour.cs:528)
UnityEngine.Debug:LogException(Exception)
Unity.Netcode.NetworkBehaviour:InternalOnNetworkDespawn() (at ./Packages/[email protected]/Runtime/Core/NetworkBehaviour.cs:532)
Unity.Netcode.NetworkObject:InvokeBehaviourNetworkDespawn() (at ./Packages/[email protected]/Runtime/Core/NetworkObject.cs:1084)
Unity.Netcode.NetworkSpawnManager:OnDespawnObject(NetworkObject, Boolean) (at ./Packages/[email protected]/Runtime/Spawning/NetworkSpawnManager.cs:849)
Unity.Netcode.NetworkObject:OnDestroy() (at ./Packages/[email protected]/Runtime/Core/NetworkObject.cs:568)

There may be a bug here to address inside of UnregisterNamedMessageHandler and/or there may be adjustments you want to make to detect and not fire off OnNetworkDespawn in cases when OnNetworkSpawn has never fired.

For now, I just am checking for an empty m_MessageName:

/// <inheritdoc/>
        public override void OnNetworkDespawn()
        {
            if (!NetworkManager.ShutdownInProgress && NetworkManager.CustomMessagingManager != null && !string.IsNullOrEmpty(m_MessageName))
            {
                NetworkManager.CustomMessagingManager.UnregisterNamedMessageHandler(m_MessageName);
            }
            CanCommitToTransform = false;
            if (NetworkManager != null && NetworkManager.NetworkTickSystem != null)
            {
                NetworkManager.NetworkTickSystem.Tick -= NetworkTickSystem_Tick;
            }
        }

[NoelStephensUnity]

Yeah, your work around is what should have been there. Nice catch and thank you for posting this issue!
👍