The problem is when I try to save a blank field in the Option, I get this error:
I could change the Data type to string, but then I would need to in the PHP convert the username to a userId. Perhaps allow a non-numeric value for this type of data?
That said, we should probably try to give a better error here. However, the problem is mostly the data type you selected and the lack of a default value.
I'll move this back solely in terms of giving a better error/preventing this exception.