title: Android Data Binding makes app crash when using include tag in a non-root ViewGroup
body: <p>When I use <code>include</code> tag in a non-root element in my xml file with <strong>Android Data Binding</strong>, app crashes. But the app works well when the <code>include</code> tag is placed in  the root element or without data binding things.</p>
  
  <p>Here is my source code, can any one help me to figure out the reason ?</p>
  
  <p><em>activity_main.xml</em></p>
  
  <pre><code>&lt;layout&gt;
  
      &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:orientation="vertical"
          tools:context=".MainActivity"&gt;
  
  
          &lt;TextView
              android:id="@+id/text_view"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:text="@string/hello_world" /&gt;
  
          &lt;LinearLayout
  
              android:layout_width="match_parent"
              android:layout_height="match_parent"&gt;
  
              &lt;include layout="@layout/include_layout" /&gt;
  
          &lt;/LinearLayout&gt;
      &lt;/LinearLayout&gt;
  &lt;/layout&gt;
  </code></pre>
  
  <hr>
  
  <p><em>MainActivity.java</em></p>
  
  <pre><code>public class MainActivity extends AppCompatActivity {
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
  
          ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
          binding.textView.setText("hello world");
      }
  }
  </code></pre>
  
  <p><em>stack trace</em></p>
  
  <pre><code>I/ActivityManager(13254): START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.liangfeizc.databindings/.MainActivity (has extras)} from uid 10008 on display 0
  I/ActivityManager(13254): Start proc com.liangfeizc.databindings for activity com.liangfeizc.databindings/.MainActivity: pid=18181 uid=10065 gids={50065, 9997} abi=x86
  I/art     (18181): Not late-enabling -Xcheck:jni (already on)
  D/AndroidRuntime(18181): Shutting down VM
  E/AndroidRuntime(18181): FATAL EXCEPTION: main
  E/AndroidRuntime(18181): Process: com.liangfeizc.databindings, PID: 18181
  E/AndroidRuntime(18181): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.liangfeizc.databindings/com.liangfeizc.databindings.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.setTag(java.lang.Object)' on a null object reference
  E/AndroidRuntime(18181):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
  E/AndroidRuntime(18181):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
  E/AndroidRuntime(18181):  at android.app.ActivityThread.access$800(ActivityThread.java:144)
  E/AndroidRuntime(18181):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
  E/AndroidRuntime(18181):  at android.os.Handler.dispatchMessage(Handler.java:102)
  E/AndroidRuntime(18181):  at android.os.Looper.loop(Looper.java:135)
  E/AndroidRuntime(18181):  at android.app.ActivityThread.main(ActivityThread.java:5221)
  E/AndroidRuntime(18181):  at java.lang.reflect.Method.invoke(Native Method)
  E/AndroidRuntime(18181):  at java.lang.reflect.Method.invoke(Method.java:372)
  E/AndroidRuntime(18181):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
  E/AndroidRuntime(18181):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  E/AndroidRuntime(18181): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.setTag(java.lang.Object)' on a null object reference
  E/AndroidRuntime(18181):  at com.liangfeizc.databindings.databinding.ActivityMainBinding.&lt;init&gt;(ActivityMainBinding.java:27)
  E/AndroidRuntime(18181):  at com.liangfeizc.databindings.databinding.ActivityMainBinding.bind(ActivityMainBinding.java:88)
  E/AndroidRuntime(18181):  at android.databinding.DataBinderMapper.getDataBinder(DataBinderMapper.java:14)
  E/AndroidRuntime(18181):  at android.databinding.DataBindingUtil.bind(DataBindingUtil.java:107)
  E/AndroidRuntime(18181):  at android.databinding.DataBindingUtil.inflate(DataBindingUtil.java:68)
  E/AndroidRuntime(18181):  at android.databinding.DataBindingUtil.setContentView(DataBindingUtil.java:185)
  E/AndroidRuntime(18181):  at com.liangfeizc.databindings.MainActivity.onCreate(MainActivity.java:18)
  E/AndroidRuntime(18181):  at android.app.Activity.performCreate(Activity.java:5937)
  E/AndroidRuntime(18181):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
  E/AndroidRuntime(18181):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
  E/AndroidRuntime(18181):  ... 10 more
  W/ActivityManager(13254):   Force finishing activity com.liangfeizc.databindings/.MainActivity
  D/        (13254): HostConnection::get() New Host Connection established 0xa0a234d0, tid 13352
  </code></pre>