Bug 1094129 - [Woodduck v2.0][Flame v2.1][Settings]There is no SIM setti...

...ngs icons when you insert SIM2 only in Settings -> Cellular & Data.
From MDN: 
navigator.mozMobileConnections returns an array of MozMobileConnection objects you can use to get information about the current mobile voice and data connection states of the device.

Let's use for-loop instead of for-in-loop to iterate array :)