title: NullPointer exception at android.support.v4.app.FragmentManagerImpl.makeInactive
body: <p>I'm seeing a weird exception in Android Support Library - the stack trace is below. Any ideas what could be causing this? I'm unable to reproduce the exception on any of my devices, but there seem to be quite a few visible in the Google Play DevConsole.</p>
  
  <pre><code>java.lang.NullPointerException
  at android.support.v4.app.FragmentManagerImpl.makeInactive(FragmentManager.java:1133)
  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1044)
  at android.support.v4.app.FragmentManagerImpl.removeFragment(FragmentManager.java:1171)
  at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:582)
  at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1416)
  at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:420)
  at android.os.Handler.handleCallback(Handler.java:608)
  at android.os.Handler.dispatchMessage(Handler.java:92)
  at android.os.Looper.loop(Looper.java:156)
  at android.app.ActivityThread.main(ActivityThread.java:5045)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:511)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
  at dalvik.system.NativeStart.main(Native Method)
  </code></pre>