You mean calling the method without 'self'??
Right, it wasn't a good idea.
A nil as an error object seems quite unusual. By now, a quite simple
solution would be to "normalize" a nil to false when calling __close.
I imagine it's rare-- though it can be achieved simply by `error()`. On the other hand, if you're writing a library, or there is 3rd party code invoked within the scope of to-be-closed, you can't really guess what error values may be used.
Normalizing to false doesn't seem better, as boolean is also a valid error value. If it's deemed worth fixing, adding a status arg seems best.
