I'm only aligning it with what is done in Contact Settings. https://github.com/mozilla-b2g/gaia/blob/master/apps/communications/contacts/js/contacts_settings.js#L108 

According to the comment found in Contact Settings 'Card should either be "ready" (connected to network) or "null" (card in phone but cannot connect to network for some reason).' but @arcturus  probably has more context than me here