Update app.py

app.py

@@ -29,7 +29,7 @@ def check_urls(url_list):
                 time.sleep(1)  # Wait for 1 second between requests
             status_codes.append(final_status_code)
         except requests.RequestException:
-            status_codes.append(None)  # Handle connection errors
+            status_codes.append(float('nan'))  # Handle connection errors
 
     df = pd.DataFrame({"URL": urls, "Status Code": status_codes})
     return df