remove unused state var

app.py

@@ -17,8 +17,6 @@ cookie_manager = get_manager()
 
 st.session_state.thread_id = cookie_manager.get('thread_id')
 
-if "start_chat" not in st.session_state:
-    st.session_state.start_chat = False
 if "session_id" not in st.session_state:
     st.session_state.session_id = str(uuid.uuid4())
 if "messages" not in st.session_state:
@@ -34,7 +32,6 @@ with st.sidebar:
     c1, c2 = st.columns(2)
 
     if c1.button("Start Chat", use_container_width=True):
-        st.session_state.start_chat = True
         if thread_id:
             st.session_state.thread_id = thread_id
         else:
@@ -47,9 +44,8 @@ with st.sidebar:
         cookie_manager.set('thread_id', st.session_state.thread_id)
 
     if c2.button("Clear Chat", use_container_width=True):
-        st.session_state.start_chat = False
-        st.session_state.thread_id = None
         cookie_manager.delete('thread_id')
+        st.session_state.thread_id = None
 
 #def process_citations(message):
 #    message_content = message.content[0].text