Change to nullable cast in LLamaSharpTextCompletion.

LLama.SemanticKernel/TextCompletion/LLamaSharpTextCompletion.cs

@@ -16,14 +16,16 @@ public sealed class LLamaSharpTextCompletion : ITextCompletion
 
     public async Task<IReadOnlyList<ITextResult>> GetCompletionsAsync(string text, AIRequestSettings? requestSettings, CancellationToken cancellationToken = default)
     {
-        var settings = (ChatRequestSettings)requestSettings;
+        var settings = (ChatRequestSettings?)requestSettings;
         var result = executor.InferAsync(text, settings?.ToLLamaSharpInferenceParams(), cancellationToken);
         return await Task.FromResult(new List<ITextResult> { new LLamaTextResult(result) }.AsReadOnly()).ConfigureAwait(false);
     }
 
+#pragma warning disable CS1998 // Async method lacks 'await' operators and will run synchronously.
     public async IAsyncEnumerable<ITextStreamingResult> GetStreamingCompletionsAsync(string text, AIRequestSettings? requestSettings, CancellationToken cancellationToken = default)
+#pragma warning restore CS1998
     {
-        var settings = (ChatRequestSettings)requestSettings;
+        var settings = (ChatRequestSettings?)requestSettings;
         var result = executor.InferAsync(text, settings?.ToLLamaSharpInferenceParams(), cancellationToken);
         yield return new LLamaTextResult(result);
     }