To reproduce:
add a SplitPane
crtl+k
add TreeView to the left AnchorPane of SplitPane trying to hit alignment lines
Following exception will be trhown:

java.lang.AssertionError: chromeMap.keySet().size()=1, lines1.size()=0, lines2.size()=2, currentLines.size()=1, newLines.size()=1, obsoleteLines.size()=1
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.guides.MovingGuideRenderer.setLines(MovingGuideRenderer.java:132)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.guides.MovingGuideController.match(MovingGuideController.java:186)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.gesture.DragGesture.dragOverGlassLayer(DragGesture.java:243)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.gesture.DragGesture.access$100(DragGesture.java:63)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.gesture.DragGesture$1.handle(DragGesture.java:105)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.gesture.DragGesture$1.handle(DragGesture.java:101)
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.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.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.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.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.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.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.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:204)
at javafx.scene.Scene$DnDGesture.fireEvent(Scene.java:2886)
at javafx.scene.Scene$DnDGesture.processTargetEnterOver(Scene.java:3042)
at javafx.scene.Scene$DnDGesture.access$6100(Scene.java:2862)
at javafx.scene.Scene$DropTargetListener.dragOver(Scene.java:2793)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$4.run(GlassSceneDnDEventHandler.java:106)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$4.run(GlassSceneDnDEventHandler.java:102)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler.handleDragOver(GlassSceneDnDEventHandler.java:102)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleDragOver(GlassViewEventHandler.java:598)
at com.sun.glass.ui.View.handleDragOver(View.java:668)
at com.sun.glass.ui.View.notifyDragOver(View.java:986)
at com.sun.glass.ui.win.WinDnDClipboard.push(Native Method)
at com.sun.glass.ui.win.WinSystemClipboard.pushToSystem(WinSystemClipboard.java:234)
at com.sun.glass.ui.SystemClipboard.flush(SystemClipboard.java:51)
at com.sun.glass.ui.ClipboardAssistance.flush(ClipboardAssistance.java:59)
at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:274)
at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1149)
at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2906)
at javafx.scene.Scene$DnDGesture.process(Scene.java:2967)
at javafx.scene.Scene$DnDGesture.access$8400(Scene.java:2862)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3700)
at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3409)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1671)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2462)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:314)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:243)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:345)
at com.sun.glass.ui.View.handleMouseEvent(View.java:526)
at com.sun.glass.ui.View.notifyMouse(View.java:898)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
at java.lang.Thread.run(Thread.java:744)