title: NullPointerException - Drawable.setBounds - probably due to fragment transitions
body: <p>I'm getting following error and I don't know why (this error is VERY RARE and not reproducable for me):</p>
  
  <pre><code>java.lang.NullPointerException: Attempt to invoke virtual method 'void android.graphics.drawable.Drawable.setBounds(int, int, int, int)' on a null object reference
  at android.widget.ImageView.animateTransform(ImageView.java:1126)
  at android.transition.ChangeImageTransform$2.set(ChangeImageTransform.java:64)
  at android.transition.ChangeImageTransform$2.set(ChangeImageTransform.java:61)
  at android.animation.PropertyValuesHolder.setAnimatedValue(PropertyValuesHolder.java:938)
  at android.animation.ObjectAnimator.animateValue(ObjectAnimator.java:952)
  at android.animation.ValueAnimator.animationFrame(ValueAnimator.java:1207)
  at android.animation.ValueAnimator.doAnimationFrame(ValueAnimator.java:1248)
  at android.animation.ValueAnimator$AnimationHandler.doAnimationFrame(ValueAnimator.java:659)
  at android.animation.ValueAnimator$AnimationHandler.run(ValueAnimator.java:682)
  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
  at android.view.Choreographer.doCallbacks(Choreographer.java:580)
  at android.view.Choreographer.doFrame(Choreographer.java:549)
  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
  at android.os.Handler.handleCallback(Handler.java:739)
  at android.os.Handler.dispatchMessage(Handler.java:95)
  at android.os.Looper.loop(Looper.java:211)
  at android.app.ActivityThread.main(ActivityThread.java:5321)
  at java.lang.reflect.Method.invoke(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:372)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1016)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:811)
  </code></pre>
  
  <p>I think it has to do with the android <code>Fragment</code> and <code>Activity</code> transitions, but I'm not sure... The above is the complete stacktrace.</p>
  
  <p>Maybe interesting, I'm using the <strong>support-library</strong></p>
  
  <p>Does anyone have an idea where this comes from and how I can prevent it?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p><strong>As written in the comments:</strong></p>
  
  <ul>
  <li><strong>I don't know from which code block this exception comes from</strong></li>
  <li><strong>I don't animate anything myself</strong></li>
  <li><strong>I assume, this problem comes from transactions between fragments (the only animations I use in my app)</strong></li>
  </ul>
  
  <p><strong>EDIT2</strong></p>
  
  <p>I did not know that I have to make sure an <code>ImageView</code> does have a content. This may lead to the above error, an <code>ImageView</code> that does not have an image yet.</p>