java.lang.NullPointerException
   at org.openide.nodes.Children$Keys.setKeys(Children.java:1487)
   at org.openide.nodes.AsynchChildren$1.add(AsynchChildren.java:187)
   at org.netbeans.modules.maven.nodes.ProjectFilesNode$ProjectFilesChildren.createKeys(ProjectFilesNode.java:178)
   at org.openide.nodes.AsynchChildren.run(AsynchChildren.java:205)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.NullPointerException
   at org.openide.util.RequestProcessor$Task.schedule(RequestProcessor.java:1452)
   at org.openide.nodes.AsynchChildren.refresh(AsynchChildren.java:133)
   at org.openide.nodes.ChildFactory.refresh(ChildFactory.java:167)
   at org.netbeans.modules.maven.nodes.ProjectFilesNode$ProjectFilesChildren.propertyChange(ProjectFilesNode.java:161)
   at java.beans.PropertyChangeSupport.fire(PropertyChangeSupport.java:335)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:327)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:263)
   at org.netbeans.modules.maven.api.NbMavenProject.doFireReload(NbMavenProject.java:486)
   at org.netbeans.modules.maven.api.NbMavenProject.access$200(NbMavenProject.java:89)
   at org.netbeans.modules.maven.api.NbMavenProject$AccessorImpl.doFireReload(NbMavenProject.java:130)
   at org.netbeans.modules.maven.NbMavenProjectImpl.fireProjectReload(NbMavenProjectImpl.java:385)
   at org.netbeans.modules.maven.NbMavenProjectImpl$1.run(NbMavenProjectImpl.java:375)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1411)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1991)