Found in version 200608141200 (M2)
While trying to surround by try and catch the following block 

SwingUtilities.invokeAndWait( new Runnable() {
                        public void run()
                        {
                            dropProperties.store();
                            // And save the project
                            try {
                                
ProjectManager.getDefault().saveProject(projectDrop);
                            }
                            catch ( IOException ex ) {
                                ErrorManager.getDefault().notify( ex );
                            }
                        }
                    });

ArrayOutOfBounds exception appears:
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
	at java.util.ArrayList.RangeCheck(ArrayList.java:547)
	at java.util.ArrayList.get(ArrayList.java:322)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.DeferredAttrList.get(DeferredAttrList.java:215)
	at org.netbeans.mdr.handlers.AttrListWrapper.get(AttrListWrapper.java:115)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.LightAttrList.get(LightAttrList.java:338)
	at 
org.netbeans.modules.editor.java.JavaKit$TryCatchAction.actionPerformed(JavaKit.java:870)
	at org.netbeans.editor.BaseAction$1.run(BaseAction.java:230)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:525)
[catch] at 
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:957)