Merge "[Settings] Reduce the operation of VoLTE config redraw"

src/com/android/settings/network/telephony/Enhanced4gBasePreferenceController.java

@@ -127,7 +127,7 @@ public class Enhanced4gBasePreferenceController extends TelephonyTogglePreferenc
 
     @Override
     public void onStart() {
-        if (mPhoneStateListener == null) {
+        if (!isModeMatched() || (mPhoneStateListener == null)) {
             return;
         }
         mPhoneStateListener.register(mContext, mSubId);
@@ -241,9 +241,11 @@ public class Enhanced4gBasePreferenceController extends TelephonyTogglePreferenc
 
         public void unregister() {
             mCallState = null;
+            if (mTelephonyManager != null) {
                 mTelephonyManager.listen(this, PhoneStateListener.LISTEN_NONE);
             }
         }
+    }
 
     /**
      * Update other preferences when 4gLte state is changed