Don't write blank baseband version

* There's no point in setting the baseband version if the returned value
  is blank anyway.

Change-Id: Ica9973a8b790c0de6afa10bc131257a3a03f18a0
Merge branch 'cm-12.0' of git://github.com/CyanogenMod/android_frameworks_opt_telephony into cm-12.0