editing a grid makes the selected row on a second grid become unselected

I worked it out.  Since the data source of the phone numbers grid was referencing an  object on the customer, updating the phone number caused the customer to update and refresh the customer grid.  Cloning the customer when it's selected from the upper grid solves the issue.  Here's an updated fiddle that shows the solution for anyone else having a similar problem.

https://jsfiddle.net/6kdvC/140/