NPE during enter transition

• Android version: 7.1.2
• Phone model: Samsung GT-I9100
• Briar version: 1.0.4 (f31219d5)

Stacktrace:

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.view.Window.getAllowReturnTransitionOverlap()' on a null object reference
        at android.app.EnterTransitionCoordinator.allowOverlappingTransitions(EnterTransitionCoordinator.java:676)
        at android.app.EnterTransitionCoordinator.sendSharedElementDestination(EnterTransitionCoordinator.java:188)
        at android.app.EnterTransitionCoordinator.viewsReady(EnterTransitionCoordinator.java:129)
        at android.app.EnterTransitionCoordinator$2.onPreDraw(EnterTransitionCoordinator.java:154)
        at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:944)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2205)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6344)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874)
        at android.view.Choreographer.doCallbacks(Choreographer.java:686)
        at android.view.Choreographer.doFrame(Choreographer.java:621)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6186)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

Unfortunately there's no clue in the stacktrace about where this crash happens. Might have been fixed by !821 (merged) if we're lucky.