Fix a potential crash in Swf.PersonaStore on destruction before preparation
Fix a potential crash in Swf.PersonaStore on destruction before preparation

If a Swf.PersonaStore is finalised before .prepare() is called, its
_contact_view member will be null, so it shouldn't try and disconnect from
signals from it.

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