Remove empty user message

Author: wieslawsoltes

src/ChatGPT.Core/ViewModels/Chat/ChatViewModel.cs

@@ -162,6 +162,11 @@ public async Task<bool> SendAsync(ChatMessageViewModel sendMessage, bool onlyAdd
 
             if (!onlyAddMessage)
             {
+                if (string.IsNullOrWhiteSpace(sendMessage.Message))
+                {
+                    Messages.Remove(sendMessage);
+                }
+                
                 var chatPrompt = CreateChatMessages();
 
                 _cts = new CancellationTokenSource();