Here are some possible resolution steps.
1) Look for any statements such as delete(obj) or clear obj that could cause the object to be deleted prematurely.
2) Double-check the logic and flow of your callback function to ensure that it correctly handles the desired behavior. Verify that any conditions or loops within the callback are properly defined and terminated to avoid unexpected errors.
3) Confirm that the object being accessed, app.zone_now, exists and is still valid at the time the callback is triggered. Check if the object is properly initialized and accessible within the scope of the callback function.
4) Debug your callback function. You can ue breakpoints to inspect the values of variables and objects at runtime. This will help identify the specific line of code causing the error and allow you to analyze the state of your application.
