report failed throwing NullPointerException invoking getProjects

running command maven site for project containing report maven-multiproject-plugin following error occurs:

multiproject:dependency-convergence-report:

BUILD FAILED
org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getProjects' in clas
s org.apache.maven.multiproject.harmonizer.MultiDependency threw exception class java.lang.NullPoint
erException : null
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:246)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:175)
at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:327)
at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:131)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:114)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:55)
at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:166)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:114)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:55)
at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:166)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:114)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230)
at org.apache.velocity.Template.merge(Template.java:256)
at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:450)
at org.apache.commons.jelly.tags.velocity.MergeTag.mergeTemplate(MergeTag.java:186)
at org.apache.commons.jelly.tags.velocity.MergeTag.doTag(MergeTag.java:68)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag.runBodyTag(MavenGoalTag.java:82)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag$MavenGoalAction.performAction(MavenGoalTag
.java:115)
at org.apache.maven.werkz.Goal.fire(Goal.java:647)
at org.apache.maven.werkz.Goal.attain(Goal.java:582)
at org.apache.maven.werkz.WerkzProject.attainGoal(WerkzProject.java:208)
at org.apache.maven.jelly.tags.werkz.MavenAttainGoalTag.doTag(MavenAttainGoalTag.java:114)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag.runBodyTag(MavenGoalTag.java:82)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag$MavenGoalAction.performAction(MavenGoalTag
.java:115)
at org.apache.maven.werkz.Goal.fire(Goal.java:647)
at org.apache.maven.werkz.Goal.attain(Goal.java:582)
at org.apache.maven.werkz.WerkzProject.attainGoal(WerkzProject.java:208)
at org.apache.maven.jelly.tags.werkz.MavenAttainGoalTag.doTag(MavenAttainGoalTag.java:114)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.tags.core.WhenTag.doTag(WhenTag.java:46)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.tags.core.ChooseTag.doTag(ChooseTag.java:38)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.tags.core.IfTag.doTag(IfTag.java:42)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.tags.core.ForEachTag.doTag(ForEachTag.java:150)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag.runBodyTag(MavenGoalTag.java:82)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag$MavenGoalAction.performAction(MavenGoalTag
.java:115)
at org.apache.maven.werkz.Goal.fire(Goal.java:647)
at org.apache.maven.werkz.Goal.attain(Goal.java:582)
at org.apache.maven.werkz.WerkzProject.attainGoal(WerkzProject.java:208)
at org.apache.maven.jelly.tags.werkz.MavenAttainGoalTag.doTag(MavenAttainGoalTag.java:114)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:250)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag.runBodyTag(MavenGoalTag.java:82)
at org.apache.maven.jelly.tags.werkz.MavenGoalTag$MavenGoalAction.performAction(MavenGoalTag
.java:115)
at org.apache.maven.werkz.Goal.fire(Goal.java:647)
at org.apache.maven.werkz.Goal.attain(Goal.java:582)
at org.apache.maven.plugin.PluginManager.attainGoals(PluginManager.java:709)
at org.apache.maven.MavenSession.attainGoals(MavenSession.java:264)
at org.apache.maven.cli.App.doMain(App.java:546)
at org.apache.maven.cli.App.main(App.java:1390)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at com.werken.forehead.Forehead.run(Forehead.java:551)
at com.werken.forehead.Forehead.main(Forehead.java:581)
File...... file:/C:/Documents and Settings/nickname/.maven/cache/maven-multiproject-plugin-1.5/plugin.
jelly
Element... velocity:merge
Line...... 380
Column.... 11
Invocation of method 'getProjects' in class org.apache.maven.multiproject.harmonizer.MultiDependenc
y threw exception class java.lang.NullPointerException : null
Total time : 16 seconds
Finished at : Wednesday, August 2, 2006 8:44:34 AM CEST

Below is content of project.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<project>
<extend>../project/project.xml</extend>
<pomVersion>3</pomVersion>
<artifactId>rfl-project-main</artifactId>
<name>RFL Project Main</name>
<groupId>$

</groupId>
<currentVersion>$

</currentVersion>
<reports>
<report>maven-faq-plugin</report>
<report>maven-multiproject-plugin</report>
</reports>
</project>