java.lang.IllegalArgumentException: Root cannot be null.
   at org.netbeans.modules.java.classpath.SimplePathResourceImplementation.verify(SimplePathResourceImplementation.java:85)
   at org.netbeans.modules.java.classpath.SimplePathResourceImplementation.verify(SimplePathResourceImplementation.java:68)
   at org.netbeans.modules.java.classpath.SimplePathResourceImplementation.<init>(SimplePathResourceImplementation.java:126)
   at org.netbeans.spi.java.classpath.support.ClassPathSupport.createResource(ClassPathSupport.java:77)
   at org.netbeans.modules.maven.classpath.EndorsedClassPathImpl.getResources(EndorsedClassPathImpl.java:128)
   at org.netbeans.modules.maven.classpath.BootClassPathImpl.getResources(BootClassPathImpl.java:97)
   at org.netbeans.api.java.classpath.ClassPath.entries(ClassPath.java:350)
   at org.netbeans.modules.parsing.impl.indexing.PathRegistry.createResources(PathRegistry.java:649)
   at org.netbeans.modules.parsing.impl.indexing.PathRegistry.getSources(PathRegistry.java:257)
   at org.netbeans.modules.parsing.impl.indexing.errors.Utilities.findIndexedRootsUnderDirectory(Utilities.java:85)
   at org.netbeans.modules.parsing.impl.indexing.errors.ErrorAnnotator$1.run(ErrorAnnotator.java:322)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1452)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2032)