If I save the listview entirely and then click Add, I don't get this error and it adds the new row.
Update: I've figured out that I can't call my unbound rules in the various listview events. I was trying to use them for validation and some of them have expressions in them. It makes me wonder what the point of those events are if I can't put anything in them, but I'm going to find another way to do do what I'm trying to do.
If anyone reading this has any idea where I can find solid documentation on the editable listview event lifecycle I'd love to see it. The documentation is really weak.
Also, you can localize the issue by setting a breakpoint on RangeError type of exception , and then adjust the code appropriately.