Based on your error, the rGroups BO is doing something that requires the CurrentRow to exist, since that is not the case "CurrentRowIndex: -1" then you get the exception.
Put some validation in your code to check for the BO.Count > 0 to avoid this kind of error.
Secondly you have something that evaluating the property probably before it has been created. This is not a complex property by any means, it is just a simple property exposing another BO. So be sure that it has been set to a value prior to evaluation and do not let it be evauluated (at least the internal properties) at design-time if an object has not been set.
I've checked DesignMode and null value.