SendNotification - Populate From

I'm attempting to populate the From field of the SendNotification by using the lookup value of Initiator. 

 I try the following:

Open the Select People and Groups Dialog

Expand the Lookup Section

Select Initiator - Click Add - Click OK

I then get a Script Error.  An error has occurred in the script on this page.  Error: Unable to get property "key" of undefined or null reference

If I pick a person from Internal Search it works fine.  Any ideas?  Thank You