Update app.py

app.py

@@ -352,6 +352,9 @@ def on_change_documents_only():
 if __name__ == '__main__':
     st.set_page_config(page_title="Multipurpose AI Agent",layout="wide", initial_sidebar_state='collapsed')
 
+    if 'menu_id' not in st.session_state:
+        st.session_state.menu_id = 'ChatBot'
+
     styles = {
         "nav": {
             "background-color": "rgb(204, 200, 194)",
@@ -375,7 +378,7 @@ if __name__ == '__main__':
     
     st.session_state.menu_id = st_navbar(
         ['ChatBot', 'Documents'], 
-        None,
+        st.session_state.menu_id,
         options={
             'hide_nav': False,
             'fix_shadow': False,