java.lang.AssertionError: LibraryFiles{, packageInfo=nullversions={1.2=[base.css, base.min.css, layout.css, skeleton.css, skeleton.min.css]}}
   at org.netbeans.modules.web.clientproject.libraries.CDNJSLibrariesProvider.readLibraries(CDNJSLibrariesProvider.java:198)
   at org.netbeans.modules.web.clientproject.libraries.CDNJSLibrariesProvider.getLibraries(CDNJSLibrariesProvider.java:118)
   at org.netbeans.modules.web.clientproject.api.WebClientLibraryManager.addLibraries(WebClientLibraryManager.java:311)
   at org.netbeans.modules.web.clientproject.api.WebClientLibraryManager.getLibraries(WebClientLibraryManager.java:219)
   at org.netbeans.modules.web.clientproject.api.jslibs.JavaScriptLibrarySelectionPanel$LibrariesTableModel$1.run(JavaScriptLibrarySelectionPanel.java:1255)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1432)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2042)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.AssertionError: LibraryFiles{, packageInfo=nullversions={1.2=[base.css, base.min.css, layout.css, skeleton.css, skeleton.min.css]}}
   at org.openide.util.RequestProcessor.post(RequestProcessor.java:424)
   at org.netbeans.modules.web.clientproject.api.jslibs.JavaScriptLibrarySelectionPanel$LibrariesTableModel.populateModel(JavaScriptLibrarySelectionPanel.java:1251)
   at org.netbeans.modules.web.clientproject.api.jslibs.JavaScriptLibrarySelectionPanel$LibrariesTableModel$2.run(JavaScriptLibrarySelectionPanel.java:1385)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
   at java.awt.EventQueue.access$200(EventQueue.java:103)
   at java.awt.EventQueue$3.run(EventQueue.java:694)
   at java.awt.EventQueue$3.run(EventQueue.java:692)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)