Bug 866690 - [Dialer] Call Log broken due to mcc being null if no SIM (r=etiennesegonzac).

If we start the device with no SIM, the Call Log does start correctly since mozMobileConnection.voice.network.mcc is null and the toString() function is invoked on it -> https://github.com/mozilla-b2g/gaia/blob/master/apps/communications/dialer/js/recents.js#L168

The problem is due to mcc being a string and not a number anymore. No need to call .toString() on it.