java.lang.RuntimeException: Unable to destroy activity {com.tac.floatingbutton/com.tac.floatingbutton.ContentActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3778)
            at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3811)
            at android.app.ActivityThread.access$1200(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1384)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:155)
            at android.app.ActivityThread.main(ActivityThread.java:5454)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1029)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:796)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.tac.eye_helper.provider.DataProviderDao.delete(DataProviderDao.java:40)
            at android.content.ContentProvider$Transport.delete(ContentProvider.java:249)
            at android.content.ContentResolver.delete(ContentResolver.java:966)
            at com.tac.eye_helper.utils.DataHelper.clearMessages(DataHelper.java:50)
            at com.tac.eye_helper.session.BasicSession.finish(BasicSession.java:56)
            at com.tac.eye_helper.session.SessionManagerImpl.finishCurrentSession(SessionManagerImpl.java:53)
            at com.tac.eye_helper.ui.ChatFragment.onDestroy(ChatFragment.java:120)
            at android.support.v4.app.Fragment.performDestroy(Fragment.java:2006)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1076)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
            at android.support.v4.app.FragmentManagerImpl.dispatchDestroy(FragmentManager.java:1954)
            at android.support.v4.app.FragmentActivity.onDestroy(FragmentActivity.java:313)
            at android.support.v7.app.ActionBarActivity.onDestroy(ActionBarActivity.java:169)
            at android.app.Activity.performDestroy(Activity.java:5255)
            at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1135)
            at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3761)
            at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3811)
            at android.app.ActivityThread.access$1200(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1384)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:155)
            at android.app.ActivityThread.main(ActivityThread.java:5454)
            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:1029)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:796)
            at dalvik.system.NativeStart.main(Native Method)