android - Starting ACTION_VIEW Activity from SherlockFragment causes NullPointerException -

i'm using sherlockfragment.
when press button call on fragment start call activity using intent, caused error web still load. when close call activity, error appear again.
i've tried replace latest android.support.v4.jar this error still same.
i've tried start call activity on way:

public class placedetailsfragment extends sherlockfragment {         //blabla        public void browsewebpage(final string url){             getsherlockactivity().startactivity(new intent(intent.action_view, uri.parse(websiteurl)));         } }  

and way

public class placedetailsfragment extends sherlockfragment {         //blabla     public void browsewebpage(final string url){          intent intent = new intent(intent.action_view, uri.parse(websiteurl));          startactivity(intent);     } } 

but still got same error logcat

05-20 11:37:28.971: e/androidruntime(1819): fatal exception: main 05-20 11:37:28.971: e/androidruntime(1819): java.lang.nullpointerexception 05-20 11:37:28.971: e/androidruntime(1819):     @ android.support.v4.app.fragmentmanagerimpl.savefragmentbasicstate(fragmentmanager.java:1576) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.support.v4.app.fragmentmanagerimpl.saveallstate(fragmentmanager.java:1617) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.support.v4.app.fragmentactivity.onsaveinstancestate(fragmentactivity.java:481) 05-20 11:37:28.971: e/androidruntime(1819):     @ com.actionbarsherlock.app.sherlockfragmentactivity.onsaveinstancestate(sherlockfragmentactivity.java:127) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.activity.performsaveinstancestate(activity.java:1137) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.instrumentation.callactivityonsaveinstancestate(instrumentation.java:1215) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.activitythread.performstopactivityinner(activitythread.java:2951) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.activitythread.handlestopactivity(activitythread.java:3010) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.activitythread.access$900(activitythread.java:130) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.activitythread$h.handlemessage(activitythread.java:1222) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.os.handler.dispatchmessage(handler.java:99) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.os.looper.loop(looper.java:137) 05-20 11:37:28.971: e/androidruntime(1819):     @ android.app.activitythread.main(activitythread.java:4745) 05-20 11:37:28.971: e/androidruntime(1819):     @ java.lang.reflect.method.invokenative(native method) 05-20 11:37:28.971: e/androidruntime(1819):     @ java.lang.reflect.method.invoke(method.java:511) 05-20 11:37:28.971: e/androidruntime(1819):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:786) 05-20 11:37:28.971: e/androidruntime(1819):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:553) 05-20 11:37:28.971: e/androidruntime(1819):     @ dalvik.system.nativestart.main(native method) 

the problem occured action_view , action_call either solution me out ?

i've found solution problem. caused using sherlockfragment viewindicator or other stuff.
fix problem, override menthod of fragment to:

@override public void onsaveinstancestate(bundle outstate) {     super.onsaveinstancestate(outstate);     setuservisiblehint(true); } 

solution found here