Fix issues in Wi-Fi NFC tag code

An NPE + multiple comments

Change-Id: I04ffe10874cc2e9aa9f68bc551b8da98eb6f1640

res/layout/write_wifi_config_to_nfc.xml

@@ -1,4 +1,19 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!--
+     Copyright (C) 2014 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
 
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
             style="@style/wifi_section">