개발중인 앱을 실행하는 도중에 바로 다른 앱을 실행하면 다음과같은 에러발생하면서 죽습니다.. 원인이 뭘까요
08-20 18:08:20.345: E/AndroidRuntime(15728): FATAL EXCEPTION: main
08-20 18:08:20.345: E/AndroidRuntime(15728): java.lang.NullPointerException
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.support.v4.app.FragmentManagerImpl.saveFragmentBasicState(FragmentManager.java:1576)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.support.v4.app.FragmentManagerImpl.saveAllState(FragmentManager.java:1617)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.support.v4.app.FragmentActivity.onSaveInstanceState(FragmentActivity.java:481)
08-20 18:08:20.345: E/AndroidRuntime(15728): at com.actionbarsherlock.app.SherlockFragmentActivity.onSaveInstanceState(SherlockFragmentActivity.java:126)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.Activity.performSaveInstanceState(Activity.java:1186)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1240)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:3319)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.ActivityThread.handleStopActivity(ActivityThread.java:3379)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.ActivityThread.access$1000(ActivityThread.java:165)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1353)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.os.Handler.dispatchMessage(Handler.java:99)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.os.Looper.loop(Looper.java:176)
08-20 18:08:20.345: E/AndroidRuntime(15728): at android.app.ActivityThread.main(ActivityThread.java:5455)
08-20 18:08:20.345: E/AndroidRuntime(15728): at java.lang.reflect.Method.invokeNative(Native Method)
08-20 18:08:20.345: E/AndroidRuntime(15728): at java.lang.reflect.Method.invoke(Method.java:525)
08-20 18:08:20.345: E/AndroidRuntime(15728): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
08-20 18:08:20.345: E/AndroidRuntime(15728): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
08-20 18:08:20.345: E/AndroidRuntime(15728): at dalvik.system.NativeStart.main(Native Method)
