Handle NPE in TelephonyManager

ITelphony service instance could be null at boot up
when device activation is taking place.

An additional NPE is handled here compared to this commit's original
form (If72622a2d22a20b1ce909134ce4c6446b132dffe):
  NPE exception handling in getDataEnabled has been backported from:
  GpsLocationProvider: Read data enabled status from TelephonyManager.
  I0333050d2a5b8d484466e1b1914dcfb9965398c9

  This addresses BUGDUMP-1125891

Change-Id: I89468a2b1cf680acb1edfa27ad1ffbfb145caede
(cherry picked from commit 05d1b23d)