Command sender still null on server-owned objects after PR #4063

[Anduil]

After commit b980ea4 (the Command system rewrite), Commands that include a NetworkConnectionToClient sender parameter no longer receive a valid sender when the Command is executed on a server-owned object (scene object or spawned without an owner), even if the Command was legitimately invoked by a client and requiresAuthority = false.

PR #4063 fixed this for objects that have a valid connectionToClient, but the problem still remains for server-owned objects where connectionToClient is naturally null.

Before the rewrite, this worked correctly:
Commands called by clients on server-owned objects could receive the sender connection.

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Reproduction

1. Create a server-owned object:

NetworkServer.Spawn(globalObj); // no owner

2. On each client (and host-client), call a Command from OnStartClient.

public class GlobalManager : NetworkBehaviour
{
    public override void OnStartClient()
    {
        base.OnStartClient();
        CmdRegisterClient();  // called from client-side of each client
    }

    [Command(requiresAuthority = false)]
    void CmdRegisterClient(NetworkConnectionToClient sender = null)
    {
        Debug.Log("Sender = " + sender);   // <-- always null for host + server object
    }
}

3. Observe on the server:
   The sender is always null because the weaver still fills it with this.connectionToClient, which is null for server-owned objects.

This happens even though the Command was called by a real client.

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Expected

Commands with requiresAuthority = false should provide the calling client's connection as the sender, same as before commit b980ea4.

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Actual

Commands on server-owned objects always receive sender == null after the rewrite.
PR #4063 fixes this only when connectionToClient is non-null (player-owned or client-owned objects), but not for server-owned ones.

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P.S. I’m not entirely sure if my understanding of the root cause is 100% correct, and I apologize if any part of this description is inaccurate.