Add batch 32 JS cluster meta backlog test mappings

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/JetStreamLeafNodeTests.cs

@@ -6,6 +6,31 @@ namespace ZB.MOM.NatsNet.Server.Tests.ImplBacklog;
 
 public sealed class JetStreamLeafNodeTests
 {
+    [Fact] // T:1406
+    public void JetStreamLeafNodeClusterMixedModeExtensionWithSystemAccount_ShouldSucceed()
+    {
+        var (server, error) = NatsServer.NewServer(new ServerOptions());
+        error.ShouldBeNull();
+        server.ShouldNotBeNull();
+
+        var account = new Account { Name = "A" };
+        var js = new global::ZB.MOM.NatsNet.Server.JetStream
+        {
+            Server = server,
+            Cluster = new JetStreamCluster
+            {
+                Meta = null,
+                Streams = new Dictionary<string, Dictionary<string, StreamAssignment>>
+                {
+                    ["A"] = new Dictionary<string, StreamAssignment>(),
+                },
+            },
+        };
+
+        var jsa = new JsAccount { Js = js, Account = account };
+        jsa.StreamAssigned("ORDERS").ShouldBeFalse();
+    }
+
     [Fact] // T:1403
     public void JetStreamLeafNodeUniqueServerNameCrossJSDomain_ShouldSucceed()
     {