Open the attached fxml file.
From the Hierarchy, select the 2nd AnchorPane and hit the Delete key: the following NPE is raised:

SEVERE: An exception was thrown:
java.lang.NullPointerException
at com.oracle.javafx.scenebuilder.kit.editor.job.DeleteSelectionJob.execute(DeleteSelectionJob.java:62)
at com.oracle.javafx.scenebuilder.kit.editor.JobManager.executeJob(JobManager.java:191)
at com.oracle.javafx.scenebuilder.kit.editor.JobManager.push(JobManager.java:80)
at com.oracle.javafx.scenebuilder.kit.editor.EditorController.performEditAction(EditorController.java:962)
at com.oracle.javafx.scenebuilder.app.DocumentWindowController.performDelete(DocumentWindowController.java:1467)
at com.oracle.javafx.scenebuilder.app.DocumentWindowController.performEditAction(DocumentWindowController.java:808)
at com.oracle.javafx.scenebuilder.app.menubar.MenuBarController$DocumentEditActionController.perform(MenuBarController.java:1569)
at com.oracle.javafx.scenebuilder.app.menubar.MenuBarController.handleOnActionMenu(MenuBarController.java:1093)
at com.oracle.javafx.scenebuilder.app.menubar.MenuBarController.lambda$1(MenuBarController.java:1087)
at com.oracle.javafx.scenebuilder.app.menubar.MenuBarController$$Lambda$71/1029944381.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
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.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
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:49)