Avoid NPE calling updateProgressBar

plus in some more callbacks.

Got this myself with recent alpha bits:
java.lang.NullPointerException: Attempt to invoke virtual method 'void org.wikipedia.page.PageActivity.updateProgressBar(boolean, boolean, int)' on a null object reference
at org.wikipedia.page.PageViewFragmentInternal.performActionForState(PageViewFragmentInternal.java:520)
at org.wikipedia.page.PageViewFragmentInternal.access$1100(PageViewFragmentInternal.java:76)
at org.wikipedia.page.PageViewFragmentInternal$5$1.run(PageViewFragmentInternal.java:405)
at org.wikipedia.ViewAnimations$2.onAnimationEnd(ViewAnimations.java:127)
at com.nineoldandroids.view.ViewPropertyAnimatorICS$1.onAnimationEnd(ViewPropertyAnimatorICS.java:90)
at android.view.ViewPropertyAnimator$AnimatorEventListener.onAnimationEnd(ViewPropertyAnimator.java:1116)
at android.animation.ValueAnimator.endAnimation(ValueAnimator.java:1089)
at android.animation.ValueAnimator$AnimationHandler.doAnimationFrame(ValueAnimator.java:666)
at android.animation.ValueAnimator$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: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)

Change-Id: Ia22b82c9e0698ca42e3f67f07f0c6467d9f552a7
Merge "Avoid NPE calling updateProgressBar"