Because of testing for falsy values `!index` would be `true` for `0`, but the intention of the caller could be to actually get the connection at index `0`.

I kept it here for compatibilty, since eventually all future calls to `getIccById` should use no parameters and rely on the index given by `DsdsSettings.getIccCardIndexForCallSettings()`. But there is a lot of code still using the manual `getIccById(index)` around and I am not sure that some of this code does actually need a particular index.

Perhaps a comment would help.