Fix compilation with -Werror=format-security
Fix compilation with -Werror=format-security

Reviewed-by: Debarshi Ray <d4138cfd8a3a9a06c7aa906ba2356c6b9e05c624@gnome.org>
Bug: https://bugzilla.gnome.org/show_bug.cgi?id=693214

halfline/gnome-online-accounts,halfline/gnome-online-accounts,ritzk/gnome-online-accounts,halfline/gnome-online-accounts,dnohales/gnome-online-accounts,ritzk/gnome-online-accounts,felipeborges/gnome-online-accounts,felipeborges/gnome-online-accounts,Distrotech/gnome-online-accounts,dnohales/gnome-online-accounts,Distrotech/gnome-online-accounts,dnohales/gnome-online-accounts,Distrotech/gnome-online-accounts,ritzk/gnome-online-accounts,felipeborges/gnome-online-accounts