Fix response generation and add error handling

app.py

@@ -124,6 +124,8 @@ if prompt := st.chat_input("What would you like to ask the Muse?"):
     with st.spinner("The Muse is contemplating..."):
         try:
             response = generate_response(prompt, tokenizer, generation_model, embedding_model, index, chunks)
+            if not response or response.isspace():
+                raise ValueError("Generated response is empty or contains only whitespace")
         except Exception as e:
             response = f"I apologize, but I encountered an error: {str(e)}"