error

Process: com.sylwke3100.freetrackgps, PID: 4945
    java.lang.NullPointerException
            at android.preference.ListPreference.findIndexOfValue(ListPreference.java:223)
            at android.preference.ListPreference.getValueIndex(ListPreference.java:232)
            at android.preference.ListPreference.getEntry(ListPreference.java:210)
            at android.preference.ListPreference.getSummary(ListPreference.java:156)
            at android.preference.Preference.onBindView(Preference.java:524)
            at android.preference.Preference.getView(Preference.java:462)
            at android.preference.PreferenceGroupAdapter.getView(PreferenceGroupAdapter.java:221)
            at android.widget.AbsListView.obtainView(AbsListView.java:2255)
            at android.widget.ListView.makeAndAddView(ListView.java:1790)
            at android.widget.ListView.fillDown(ListView.java:691)
            at android.widget.ListView.fillFromTop(ListView.java:752)
            at android.widget.ListView.layoutChildren(ListView.java:1630)
            at android.widget.AbsListView.onLayout(AbsListView.java:2087)
            at android.view.View.layout(View.java:14841)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1717)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1571)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1480)
            at android.view.View.layout(View.java:14841)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
            at android.view.View.layout(View.java:14841)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:374)
            at android.view.View.layout(View.java:14841)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
            at android.view.View.layout(View.java:14841)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1986)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1743)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5603)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
            at android.view.Choreographer.doCallbacks(Choreographer.java:574)
            at android.view.Choreographer.doFrame(Choreographer.java:544)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)