Hi Bruce!
You are not bothering at all 🙂
I think I know where the problem is – I forgot to add an check for empty values in one of the code part, which converts the number to the formatted number, so it breaks on empty values.
I’ve made a tiny modification to the final code, this should account for empty inputs as well, and treat them as 0 value:
I hope this gets rid of the error messages 🙂