Update app.py

app.py

@@ -57,8 +57,8 @@ my_system_instructions = "You are a helpful assistant. Be brief and concise. Pro
 first_message = "Hello, how can I help you today?"
 
 def delete_chat_messages():
-    for key in st.session_state.keys():
-        if key != "my_rag_text" and key != "my_system_instructions":
+    for key in list(st.session_state.keys()):
+        if key not in {"my_rag_text", "my_system_instructions", "my_llm_model", "my_space"}:
             del st.session_state[key]
     update_llm_model()