NullPointerException in descriptor goal

@Mojo( name = "aggregate-add-third-party", requiresProject = true, aggregator = true,
       defaultPhase = LifecyclePhase.GENERATE_RESOURCES )
@Execute( goal = "add-third-party" )

Caused by: java.lang.NullPointerException
	at org.apache.maven.tools.plugin.annotations.JavaAnnotationsMojoDescriptorExtractor.toMojoDescriptors(JavaAnnotationsMojoDescriptorExtractor.java:522)
	at org.apache.maven.tools.plugin.annotations.JavaAnnotationsMojoDescriptorExtractor.execute(JavaAnnotationsMojoDescriptorExtractor.java:110)
	at org.apache.maven.tools.plugin.scanner.DefaultMojoScanner.populatePluginDescriptor(DefaultMojoScanner.java:108)
	at org.apache.maven.plugin.plugin.AbstractGeneratorMojo.execute(AbstractGeneratorMojo.java:245)
	at org.apache.maven.plugin.plugin.HelpGeneratorMojo.execute(HelpGeneratorMojo.java:88)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
	... 20 more

if ( execute != null )
{
    mojoDescriptor.setExecuteGoal( execute.goal() );
    mojoDescriptor.setExecuteLifecycle( execute.lifecycle() );
    mojoDescriptor.setExecutePhase( execute.phase().id() );
}

if ( execute != null )
{
    mojoDescriptor.setExecuteGoal( execute.goal() );
    mojoDescriptor.setExecuteLifecycle( execute.lifecycle() );
    if ( execute.phase() != null )
    {
        mojoDescriptor.setExecutePhase( execute.phase().id() );
    }
}