FULL PRODUCT VERSION :
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b18)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b18, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.10240]

A DESCRIPTION OF THE PROBLEM :
This report is providing additional information to the bug JDK-8144162.

Here's how to reproduce: https://gist.github.com/micheljung/ff146e904ef02b89d14f


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the program

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
No exception
ACTUAL -
An exception

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.NullPointerException
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.getThumb(ScrollBarThemeImpl.java:409)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.thumbPosition(ScrollBarThemeImpl.java:293)
at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.getThumbPosition(ScrollBarThemeImpl.java:389)
at com.sun.webkit.WebPage.twkExecuteScript(Native Method)
at com.sun.webkit.WebPage.executeScript(WebPage.java:1439)
at javafx.scene.web.WebEngine.executeScript(WebEngine.java:982)
at sample.JDK8144162.lambda$null$0(JDK8144162.java:18)
at com.sun.javafx.application.PlatformImpl.lambda$null$174(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$175(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$149(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.application.Platform;
import javafx.concurrent.Worker;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebView;
import javafx.stage.Stage;

public class JDK8144162 extends Application {


  @Override
  public void start(Stage primaryStage) throws Exception {
    WebEngine engine = new WebView().getEngine();
    engine.getLoadWorker().stateProperty().addListener((observable, oldValue, newValue) -> {
      if (Worker.State.SUCCEEDED.equals(newValue)) {
        Platform.runLater(() -> engine.executeScript("window.scrollTo(0, document.documentElement.scrollHeight);"));
      }
    });
    engine.load("http://www.google.com");
  }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Make sure the WebView is added to the scene graph, otherwise don't call executeScript()