java.util.ConcurrentModificationException
        at java.util.IdentityHashMap$IdentityHashMapIterator.nextIndex(IdentityHashMap.java:706)
        at java.util.IdentityHashMap$KeyIterator.next(IdentityHashMap.java:795)
        at org.netbeans.spi.looks.Look.fireUniversal(Look.java:586)
        at org.netbeans.spi.looks.Look.fireChange(Look.java:523)
        at org.netbeans.spi.looks.ProxyLook$ProxyLookEventTranslator.change(ProxyLook.java:1186)
        at org.netbeans.spi.looks.Look.fireUniversal(Look.java:601)
        at org.netbeans.spi.looks.Look.fireChange(Look.java:523)
        at org.netbeans.spi.looks.ProxyLook$ProxyLookEventTranslator.change(ProxyLook.java:1186)
        at org.netbeans.spi.looks.Look.fireUniversal(Look.java:601)
        at org.netbeans.spi.looks.Look.fireChange(Look.java:523)
        at org.netbeans.spi.looks.ProxyLook$ProxyLookEventTranslator.change(ProxyLook.java:1186)
        at org.netbeans.spi.looks.Look.fireUniversal(Look.java:601)
        at org.netbeans.spi.looks.Look.fireChange(Look.java:523)
        at org.netbeans.modules.projects.ide.ui.looks.DataObjectLook$FolderLook.access$001(DataObjectLook.java:86)
        at org.netbeans.modules.projects.ide.ui.looks.DataObjectLook$1.run(DataObjectLook.java:121)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
[catch] at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)