empathy_account_settings_has_account: cope with priv->account being NULL
empathy_account_settings_has_account: cope with priv->account being NULL

priv->account is not garantee to be set so empathy_account_settings_has_account
shouldn't assume it is (#610942).

Distrotech/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets