It's happening inside the Android framework, and so hard to understand either what's causing it, or how to fix it or workaround it. The exceptions are being logged from customer usage - I cannot reproduce the error, and customer reports are anonymous so I cannot ask them for more details.
java.lang.NullPointerException
at android.widget.PopupWindow$PopupViewContainer.dispatchKeyEvent(PopupWindow.java:1359)
at android.view.ViewRoot.deliverKeyEventToViewHierarchy(ViewRoot.java:2471)
at android.view.ViewRoot.deliverKeyEvent(ViewRoot.java:2431)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1741)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:871)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)
at dalvik.system.NativeStart.main(Native Method)