BadTokenException in RestAPI

[Zillode]

android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@43237e58 is not valid; is your activity running?
at android.view.ViewRootImpl.setView(ViewRootImpl.java:536)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:259)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
at android.app.Dialog.show(Dialog.java:294)
at android.app.AlertDialog$Builder.show(AlertDialog.java:966)
at com.nutomic.syncthingandroid.syncthing.RestApi.requireRestart(RestApi.java:369)
at com.nutomic.syncthingandroid.syncthing.RestApi$10.onDeviceIdNormalized(RestApi.java:744)
at com.nutomic.syncthingandroid.syncthing.RestApi$11.onPostExecute(RestApi.java:889)
at com.nutomic.syncthingandroid.syncthing.RestApi$11.onPostExecute(RestApi.java:876)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:212)
at android.app.ActivityThread.main(ActivityThread.java:5135)
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:878)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
at dalvik.system.NativeStart.main(Native Method)