Main Activity is Null when reopen

[WingOfFlame]

happens on Android 6.0.1

also CA is installed each time

E/AndroidRuntime: FATAL EXCEPTION: main
                                                                  Process: com.PrivacyGuard, PID: 25500
                                                                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.PrivacyGuard/com.PrivacyGuard.Application.Activities.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.PrivacyGuard.Application.Network.FakeVPN.MyVpnService.stopVPN()' on a null object reference
                                                                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2464)
                                                                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524)
                                                                      at android.app.ActivityThread.access$900(ActivityThread.java:154)
                                                                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
                                                                      at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                      at android.os.Looper.loop(Looper.java:234)
                                                                      at android.app.ActivityThread.main(ActivityThread.java:5526)
                                                                      at java.lang.reflect.Method.invoke(Native Method)
                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.PrivacyGuard.Application.Network.FakeVPN.MyVpnService.stopVPN()' on a null object reference
                                                                      at com.PrivacyGuard.Application.Activities.MainActivity.stopVPN(MainActivity.java:263)
                                                                      at com.PrivacyGuard.Application.Activities.MainActivity.access$300(MainActivity.java:52)
                                                                      at com.PrivacyGuard.Application.Activities.MainActivity$1.onCheckedChanged(MainActivity.java:92)
                                                                      at android.widget.CompoundButton.setChecked(CompoundButton.java:156)
                                                                      at android.widget.ToggleButton.setChecked(ToggleButton.java:71)
                                                                      at com.PrivacyGuard.Application.Activities.MainActivity.onStart(MainActivity.java:127)
                                                                      at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1238)
                                                                      at android.app.Activity.performStart(Activity.java:6302)
                                                                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2427)
                                                                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524) 
                                                                      at android.app.ActivityThread.access$900(ActivityThread.java:154) 
                                                                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391) 
                                                                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                      at android.os.Looper.loop(Looper.java:234) 
                                                                      at android.app.ActivityThread.main(ActivityThread.java:5526) 
                                                                      at java.lang.reflect.Method.invoke(Native Method) 
                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)