Work around dotnet/fsharp#16524

Emulsion/Xmpp/XmppMessageSystem.fs

@@ -11,7 +11,7 @@ open Emulsion.Settings
 type XmppMessageSystem(ctx: ServiceContext, cancellationToken: CancellationToken, settings: XmppSettings) =
     inherit MessageSystemBase(ctx, cancellationToken)
 
-    let client = ref None
+    let mutable client = None
 
     member private _.BaseRunAsync r = base.RunAsync r
 
@@ -21,20 +21,20 @@ type XmppMessageSystem(ctx: ServiceContext, cancellationToken: CancellationToken
         let newClient = SharpXmppClient.wrap sharpXmpp |> EmulsionXmpp.initializeLogging ctx.Logger
         use newClientLifetimeDef = Lifetime.Define()
         try
-            Volatile.Write(client, Some (newClient, newClientLifetimeDef.Lifetime))
+            Volatile.Write(&client, Some (newClient, newClientLifetimeDef.Lifetime))
             do! this.BaseRunAsync receiver
         finally
-            Volatile.Write(client, None)
+            Volatile.Write(&client, None)
     }
 
     override _.RunUntilError receiver = async {
-        match Volatile.Read client with
+        match Volatile.Read &client with
         | Some(client, _) -> return! EmulsionXmpp.run settings ctx.Logger client receiver
         | None -> return failwith "The system cannot be run: the connection is not established"
     }
 
     override _.Send (OutgoingMessage message) = async {
-        match Volatile.Read(client) with
+        match Volatile.Read &client with
         | None -> failwith "Client is offline"
         | Some (client, lt) ->
             return! EmulsionXmpp.send ctx.Logger client lt settings message