java.lang.NullPointerException

[nextflex]

Any ideas for this exception?

java.lang.NullPointerException
    at android.support.v4.app.Fragment.setUserVisibleHint(Fragment.java:879)
    at android.support.v4.app.FragmentStatePagerAdapter.setPrimaryItem(FragmentStatePagerAdapter.java:152)
    at android.support.v4.view.ViewPager.populate(ViewPager.java:1104)
    at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:552)
    at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:514)
    at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:495)
    at com.astuetz.PagerSlidingTabStrip$2.onClick(PagerSlidingTabStrip.java:251)
    at android.view.View.performClick(View.java:4278)
    at android.view.View$PerformClick.run(View.java:17429)
    at android.os.Handler.handleCallback(Handler.java:725)
    at android.os.Handler.dispatchMessage(Handler.java:92)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5099)
    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:803)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:570)
    at dalvik.system.NativeStart.main(Native Method)