Add explicit null check for _connector before ReadBatchAsync

Improved safety by adding an explicit null check for _connector
before calling ReadBatchAsync in SortIdentitiesAsync. This change
clarifies intent and prevents potential null reference issues.

Author: PTKu

src/AXSharp.connectors/src/AXSharp.Connector/Identity/TwinIdentityProvider.cs

@@ -250,7 +250,10 @@ internal async Task SortIdentitiesAsync()
         await Task.Run(async () =>
         {
             _connector?.Logger.Information("Sorting identities...");
-            await _connector?.ReadBatchAsync(_identities.Select(p => p.Key), eAccessPriority.High);
+            if (_connector != null)
+            {
+                await _connector?.ReadBatchAsync(_identities.Select(p => p.Key), eAccessPriority.High);
+            }
             _sortedIdentities.Clear();
             foreach (var identity in _identities)
             {