Unable to execute "run-forked" goal with overlays

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.500s
[INFO] Finished at: Tue Oct 25 08:35:54 CEST 2011
[INFO] Final Memory: 9M/24M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.mortbay.jetty:jetty-maven-plugin:8.0.3.v20111011:run-forked (start-jetty) on project myapp-integration-tests: Failed to create Jetty process: Prepare webapp configuration: NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.mortbay.jetty:jetty-maven-plugin:8.0.3.v20111011:run-forked (start-jetty) on project myapp-integration-tests: Failed to create Jetty process
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:217)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:319)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
	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:597)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
Caused by: org.apache.maven.plugin.MojoExecutionException: Failed to create Jetty process
	at org.mortbay.jetty.plugin.JettyRunForkedMojo.startJettyRunner(JettyRunForkedMojo.java:578)
	at org.mortbay.jetty.plugin.JettyRunForkedMojo.execute(JettyRunForkedMojo.java:271)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
	... 19 more
Caused by: org.apache.maven.plugin.MojoExecutionException: Prepare webapp configuration
	at org.mortbay.jetty.plugin.JettyRunForkedMojo.prepareConfiguration(JettyRunForkedMojo.java:387)
	at org.mortbay.jetty.plugin.JettyRunForkedMojo.startJettyRunner(JettyRunForkedMojo.java:506)
	... 22 more
Caused by: java.lang.NullPointerException
	at org.mortbay.jetty.plugin.JettyRunForkedMojo.prepareConfiguration(JettyRunForkedMojo.java:376)
	... 23 more