title: Using ViewGroup throws NullPointerException
body: <p>Does anyone have a clue what could be causing this?</p>
  
  <pre><code>11-16 16:23:26.745: ERROR/AndroidRuntime(9549): Uncaught handler: thread main exiting due to uncaught exception
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549): java.lang.NullPointerException
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:692)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:692)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.view.ViewRoot.performTraversals(ViewRoot.java:722)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1658)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.os.Handler.dispatchMessage(Handler.java:99)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.os.Looper.loop(Looper.java:123)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at android.app.ActivityThread.main(ActivityThread.java:4363)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at java.lang.reflect.Method.invokeNative(Native Method)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at java.lang.reflect.Method.invoke(Method.java:521)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:862)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
  11-16 16:23:26.765: ERROR/AndroidRuntime(9549):     at dalvik.system.NativeStart.main(Native Method)
  </code></pre>