check ntpserver as empty string instead of null
check ntpserver as empty string instead of null

mServer cannot set null, because string from resource always returns
non-null charsequence

Change-Id: I8d6a6fdbc34267ee361e7bd20719887268161870
Signed-off-by: Young-Ho Cha <f1f8667db13e02d63e57947edf3fdfaa80cd9a11@gmail.com>

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base