java.lang.NullPointerException
        at org.netbeans.modules.maven.nodes.SourcesNodeFactory$NList.node(SourcesNodeFactory.java:100)
        at org.netbeans.modules.maven.nodes.SourcesNodeFactory$NList.node(SourcesNodeFactory.java:80)
        at org.netbeans.spi.project.ui.support.NodeFactorySupport$DelegateChildren.createNodes(NodeFactorySupport.java:142)
        at org.netbeans.spi.project.ui.support.NodeFactorySupport$DelegateChildren.createNodes(NodeFactorySupport.java:120)
        at org.openide.nodes.Children$Keys$KE.nodes(Children.java:1609)
        at org.openide.nodes.ChildrenArray.nodesFor(ChildrenArray.java:168)
        at org.openide.nodes.EntrySupport$Default$Info.nodes(EntrySupport.java:916)
        at org.openide.nodes.EntrySupport$Default.justComputeNodes(EntrySupport.java:244)
        at org.openide.nodes.ChildrenArray.nodes(ChildrenArray.java:101)
        at org.openide.nodes.EntrySupport$Default.getNodes(EntrySupport.java:173)
        at org.openide.nodes.EntrySupport$Default.snapshot(EntrySupport.java:139)
        at org.openide.nodes.Children.snapshot(Children.java:503)
        at org.openide.nodes.NodeMemberEvent.<init>(NodeMemberEvent.java:84)
        at org.openide.nodes.Node.fireSubNodesChange(Node.java:1087)
        at org.openide.nodes.EntrySupport$Default.notifyRemove(EntrySupport.java:647)
        at org.openide.nodes.EntrySupport$Default.updateRemove(EntrySupport.java:379)
        at org.openide.nodes.EntrySupport$Default.setEntries(EntrySupport.java:333)
        at org.openide.nodes.Children$Keys$2.run(Children.java:1503)
        at org.openide.util.Mutex$1Exec.run(Mutex.java:1239)
        at org.openide.nodes.Children$ProjectManagerDeadlockDetector.execute(Children.java:1810)
        at org.openide.util.Mutex.postRequest(Mutex.java:1245)
        at org.openide.util.Mutex.postRequest(Mutex.java:1209)
        at org.openide.util.Mutex.postWriteRequest(Mutex.java:582)
        at org.openide.nodes.Children$Keys.applyKeys(Children.java:1512)
        at org.openide.nodes.Children$Keys.setKeys(Children.java:1456)
        at org.netbeans.spi.project.ui.support.NodeFactorySupport$DelegateChildren.access$200(NodeFactorySupport.java:120)
        at org.netbeans.spi.project.ui.support.NodeFactorySupport$DelegateChildren$RunnableImpl.run(NodeFactorySupport.java:283)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:300)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:210)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:200)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:195)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:187)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)