Fix NullPointerException, TelephonyManager.getServiceState is null

Add the null protect for TelephonyManager.getServiceState.

Bug: 166676020
Test: 1. make RunSettingsRoboTests ROBOTEST_FILTER=\
RenameMobileNetworkDialogFragmentTest (PASS)
2. make RunSettingsRoboTests ROBOTEST_FILTER=\
AutoSelectPreferenceControllerTest (PASS)
3. make RunSettingsRoboTests ROBOTEST_FILTER=\
PreferredNetworkModePreferenceControllerTest (PASS)
4. make RunSettingsRoboTests ROBOTEST_FILTER=\
EnabledNetworkModePreferenceControllerTest (PASS)

Change-Id: I61e59f7ba9d6c64019d620d6cb80099ded41473f
Merged-In: I61e59f7ba9d6c64019d620d6cb80099ded41473f