Test GetChildAtIndex for an empty registry
Test GetChildAtIndex for an empty registry

In the registryd tests, we don't yet have a way to populate it with
mock accessible apps.  Anyway, those are hopefully tested in the
at-spi2-atk.

GNOME/at-spi2-core,GNOME/at-spi2-core,GNOME/at-spi2-core