title: Shared element activity transition on android 5
body: <p>I wanted to setup a shared element transition when going from one Activity to another. </p>
  
  <p>The first Activity has a RecyclerView with items. When an item is clicked that item should animate to the new activity. </p>
  
  <p>So i've set a 
          android:transitionName="item" on both the final activity views, as wel as the recycler-view item views. </p>
  
  <p>I'm also using this code when going to the next activity:</p>
  
  <pre><code>this.startActivity(intent, ActivityOptions.makeSceneTransitionAnimation(this, itemView, "boomrang_item").toBundle());
  </code></pre>
  
  <p>When clicking an item, it transitions properly and the new view is shown. It is really nice.
  However when i click the back button. Sometimes it works fine, but most of the time my activity crashes with the following stacktrace:</p>
  
  <pre><code>   java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.ViewGroup.transformMatrixToGlobal(android.graphics.Matrix)' on a null object reference
              at android.view.GhostView.calculateMatrix(GhostView.java:95)
              at android.app.ActivityTransitionCoordinator$GhostViewListeners.onPreDraw(ActivityTransitionCoordinator.java:845)
              at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:847)
              at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1956)
              at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
              at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
              at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
              at android.view.Choreographer.doCallbacks(Choreographer.java:580)
              at android.view.Choreographer.doFrame(Choreographer.java:550)
              at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
              at android.os.Handler.handleCallback(Handler.java:739)
              at android.os.Handler.dispatchMessage(Handler.java:95)
              at android.os.Looper.loop(Looper.java:135)
              at android.app.ActivityThread.main(ActivityThread.java:5221)
              at java.lang.reflect.Method.invoke(Native Method)
              at java.lang.reflect.Method.invoke(Method.java:372)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  </code></pre>
  
  <p>What am i doing wrong?
  It looks like a bug in android 5</p>