Got NPE in XSD editor design view.  Steps to reproduce:
1. Create a new XSD
2. Add an element declaration in schema view
3. Go to design view
4. Expand the element declaration (no child components for now)
5. Drag and drop a new element declaration as the child of the existing 
element declaration
6. Drag a new element declaration as the sibling of the one just added and 
drop to the beginning of the model group.
7. Save the XSD
8. Close the XSD editor window
9. Double click the XSD to open it in XSD editor again
10. Go to design view
11. Expand the global element declaration (it should have two child element 
declarations)
12. Drag a new element declaration and drop it to the beginning of the model 
group of the global element declaration.  NPE occurs at this time.

Video is also attached.

Stack trace:

java.lang.NullPointerException
   at 
org.netbeans.modules.xml.schema.abe.ElementsContainerPanel$1._propertyChange
(ElementsContainerPanel.java:62)
   at org.netbeans.modules.xml.schema.abe.ModelEventMediator.propertyChange
(ModelEventMediator.java:55)
   at 
org.netbeans.modules.xml.xam.AbstractComponent$DelegateListener.propertyChange
(AbstractComponent.java:401)
   at java.beans.PropertyChangeSupport.firePropertyChange
(PropertyChangeSupport.java:333)
   at 
org.netbeans.modules.xml.xam.AbstractModel$Transaction.fireCompleteEventSet
(AbstractModel.java:401)
   at org.netbeans.modules.xml.xam.AbstractModel$Transaction.fireEvents
(AbstractModel.java:389)
   at org.netbeans.modules.xml.xam.AbstractModel.endTransaction
(AbstractModel.java:292)
   at org.netbeans.modules.xml.xam.AbstractModel.endTransaction
(AbstractModel.java:284)
   at 
org.netbeans.modules.xml.schema.abe.ElementsContainerPanel.addNewElementAt
(ElementsContainerPanel.java:195)
   at org.netbeans.modules.xml.schema.abe.ElementsContainerPanel.tweenerDrop
(ElementsContainerPanel.java:208)
   at org.netbeans.modules.xml.schema.abe.CompositorPanel.tweenerDrop
(CompositorPanel.java:537)
   at org.netbeans.modules.xml.schema.abe.ContainerPanel$2.drop
(ContainerPanel.java:429)
   at org.netbeans.modules.xml.schema.abe.TweenerPanel.drop
(TweenerPanel.java:223)
   at org.netbeans.modules.xml.schema.abe.ABEBaseDropPanel$2.drop
(ABEBaseDropPanel.java:109)
   at java.awt.dnd.DropTarget.drop(DropTarget.java:430)
   at sun.awt.dnd.SunDropTargetContextPeer.processDropMessage
(SunDropTargetContextPeer.java:500)
   at sun.awt.dnd.SunDropTargetContextPeer.access$800
(SunDropTargetContextPeer.java:53)
   at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchDropEvent
(SunDropTargetContextPeer.java:812)
   at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent
(SunDropTargetContextPeer.java:736)
   at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:29)
   at java.awt.Component.dispatchEventImpl(Component.java:3826)
   at java.awt.Container.dispatchEventImpl(Container.java:2024)
   at java.awt.Component.dispatchEvent(Component.java:3803)
   at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
   at java.awt.LightweightDispatcher.processDropTargetEvent
(Container.java:3963)
   at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3817)
   at java.awt.Container.dispatchEventImpl(Container.java:2010)
   at java.awt.Window.dispatchEventImpl(Window.java:1778)
   at java.awt.Component.dispatchEvent(Component.java:3803)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
[catch] at java.awt.EventDispatchThread.pumpOneEventForHierarchy
(EventDispatchThread.java:242)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy
(EventDispatchThread.java:163)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)