key-file: Allow empty Kf.Personas to be added to the persona store
key-file: Allow empty Kf.Personas to be added to the persona store

This is necessary for the tests for bgo#653777. It removes the error which
would previously be thrown when trying to add a persona to Kf.PersonaStore
with no properties.

Helps: bgo#653777

GNOME/folks,renatofilho/folks2,renatofilho/folks2,pwithnall/folks,renatofilho/folks,renatofilho/folks2,pwithnall/folks,GNOME/folks,renatofilho/folks,renatofilho/folks,pwithnall/folks,renatofilho/folks,renatofilho/folks2,GNOME/folks