Mouse hover on Webview scroll bar throws NPE (Call stack below)
Steps to re-produce
1. Use Simple HelloWebview and load any webpage which is greater than Webview's width and height
2. Hover Mouse on Webview scrollbar
3. observer the exception in console


This could be due to JDK-8157684 (scroll bar not showing) and JDK-8158659
java.lang.NullPointerException
        at com.sun.javafx.webkit.theme.ScrollBarThemeImpl.hitTest(ScrollBarThemeImpl.java:225)
        at com.sun.webkit.WebPage.twkProcessMouseEvent(Native Method)
        at com.sun.webkit.WebPage.dispatchMouseEvent(WebPage.java:789)
        at javafx.scene.web.WebView.processMouseEvent(WebView.java:1050)
        at javafx.scene.web.WebView.lambda$registerEventHandlers$3(WebView.java:1173)
        at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
        at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
        at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
        at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
        at javafx.event.Event.fireEvent(Event.java:198)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3868)
        at javafx.scene.Scene$MouseHandler.access$1300(Scene.java:3596)
        at javafx.scene.Scene.processMouseEvent(Scene.java:1867)
        at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2605)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:382)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
        at java.security.AccessController.doPrivileged(Native Method)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:418)
        at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:417)
        at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
        at com.sun.glass.ui.View.notifyMouse(View.java:937)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:189)
        at java.lang.Thread.run(Thread.java:804)