Update download button logic in app.py: modify the export file availability check to ensure the download button is only shown when the export file exists, improving user experience and preventing errors during download attempts.

app.py

@@ -939,10 +939,10 @@ with tab3:
                                 if col not in excluded_cols:
                                     st.session_state['export_file'][col] = st.session_state['export_file'][col].map(st.session_state['export_dict'])
                             st.write('Export portfolio updated!')
-                            try:    
-                                st.download_button(label="Download Portfolio", data=st.session_state['export_file'].to_csv(index=False), file_name="portfolio.csv", mime="text/csv")
-                            except:
-                                st.error("No portfolio to download")
+            if 'export_file' in st.session_state:    
+                st.download_button(label="Download Portfolio", data=st.session_state['export_file'].to_csv(index=False), file_name="portfolio.csv", mime="text/csv")
+            else:
+                st.error("No portfolio to download")
             
             # Add pagination controls below the dataframe
             total_rows = len(st.session_state['portfolio'])