NPE during webview shutdown

[Lior Yaffe]

After calling Platform.exit() of a webview running inside a Java FX frame
we sometimes see the following Exception in the console printed one or more
times without any functional impact:

Exception in thread "jfx" java.lang.NullPointerException
at
com.sun.javafx.tk.quantum.QuantumToolkit.isSupported(QuantumToolkit.java:1164)
at
com.sun.javafx.application.PlatformImpl.isSupportedImpl(PlatformImpl.java:954)
at
com.sun.javafx.application.PlatformImpl.isSupported(PlatformImpl.java:627)
at javafx.application.Platform.isSupported(Platform.java:250)
at
com.sun.javafx.scene.input.PickResultChooser.processOffer(PickResultChooser.java:182)
at
com.sun.javafx.scene.input.PickResultChooser.offer(PickResultChooser.java:143)
at javafx.scene.Node.doComputeIntersects(Node.java:5252)
at javafx.scene.Node.access$600(Node.java:398)
at javafx.scene.Node$1.doComputeIntersects(Node.java:456)
at
com.sun.javafx.scene.NodeHelper.computeIntersectsImpl(NodeHelper.java:180)
at com.sun.javafx.scene.NodeHelper.computeIntersects(NodeHelper.java:133)
at javafx.scene.Node.intersects(Node.java:5223)
at javafx.scene.Node$1.intersects(Node.java:543)
at com.sun.javafx.scene.NodeHelper.intersects(NodeHelper.java:258)
at javafx.scene.web.WebView.doPickNodeLocal(WebView.java:1214)
at javafx.scene.web.WebView.access$2800(WebView.java:101)
at javafx.scene.web.WebView$11.doPickNodeLocal(WebView.java:1301)
at
com.sun.java.scene.web.WebViewHelper.pickNodeLocalImpl(WebViewHelper.java:89)
at com.sun.javafx.scene.NodeHelper.pickNodeLocal(NodeHelper.java:128)
at javafx.scene.Node.pickNode(Node.java:5192)
at javafx.scene.Scene$MouseHandler.pickNode(Scene.java:3993)
at javafx.scene.Scene$MouseHandler.access$1300(Scene.java:3579)
at javafx.scene.Scene.pick(Scene.java:2029)
at javafx.scene.Scene.access$6800(Scene.java:172)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3805)
at javafx.scene.Scene$MouseHandler.access$1200(Scene.java:3579)
at javafx.scene.Scene.processMouseEvent(Scene.java:1849)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2588)
at
com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
at
com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at
java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at
com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434)
at
com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:390)
at
com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
at com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at com.sun.glass.ui.View.notifyMouse(View.java:942)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at
com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:830)

This Exception appears in several past bug reports as fixed but I can still
reproduce it with all versions.