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:156)
        at org.openide.nodes.EntrySupport$Default$Info.nodes(EntrySupport.java:920)
        at org.openide.nodes.EntrySupport$Default.updateAdd(EntrySupport.java:499)
        at org.openide.nodes.EntrySupport$Default.setEntries(EntrySupport.java:343)
        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:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)