Fix crash in gnomekeyringk.item_get_attributes_sync
Fix crash in gnomekeyringk.item_get_attributes_sync

This was crashing when requesting attributes from a keyring that doesn't
exist.

https://bugzilla.gnome.org/show_bug.cgi?id=598835

dieterv/gnome-python-desktop,dieterv/gnome-python-desktop,dieterv/gnome-python-desktop