tests: Fix logic when testing for empty state set
tests: Fix logic when testing for empty state set

https://bugzilla.gnome.org/show_bug.cgi?id=696466

Distrotech/atk,GNOME/at-spi2-core,Distrotech/atk,GNOME/at-spi2-core,GNOME/at-spi2-core,Distrotech/atk