Update app.py

app.py

@@ -40,6 +40,10 @@ def get_context_by_model(model_name):
     return model_context_limits.get(model_name, None)
 
 def get_messages_formatter_type(model_name):
+    if model_name is None:
+        logging.warning("Model name is None. Defaulting to CHATML formatter.")
+        return MessagesFormatterType.CHATML
+    
     model_name = model_name.lower()
     if "mistral" in model_name:
         return MessagesFormatterType.MISTRAL
@@ -95,6 +99,10 @@ def respond(
     top_k,
     repeat_penalty,
 ):
+    if model is None:
+        logging.error("Model is None. Please select a valid model.")
+        return "Error: No model selected. Please choose a valid model."
+
     global llm
     global llm_model
     chat_template = get_messages_formatter_type(model)
@@ -193,7 +201,7 @@ demo = gr.ChatInterface(
         gr.Dropdown([
             'Mistral-7B-Instruct-v0.3'
         ],
-            value="Mistral-7B-Instruct-v0.3",
+            value="Mistral-7B-Instruct-v0.3",  # This should match exactly
             label="Model"
         ),
         gr.Textbox(value=web_search_system_prompt, label="System message"),