Update app.py

Added condition

app.py

@@ -68,6 +68,10 @@ def chatbot(user_input,history_state,temprature_slider,  session_id=str(uuid.uui
     Function to handle user input and generate a response.
     It maintains the session history and returns the response.
     """
+    
+    if(user_input.strip() == ""):
+        return "Please enter a valid question."
+        
     llm.temperature = temprature_slider  # Set the temperature for the model
     
     response = chain.invoke(