PR: MNG-316

Submitted by:	Kenney Westerhof
Reviewed by:	Brett Porter
fix NPE when there is no default plugin configuration


git-svn-id: https://svn.apache.org/repos/asf/maven/components/trunk@163981 13f79535-47bb-0310-9956-ffa450edef68

maven-core/src/main/java/org/apache/maven/util/Xpp3DomUtils.java

@@ -30,6 +30,11 @@ private static void mergeIntoXpp3Dom( Xpp3Dom dominant, Xpp3Dom recessive )
     {
         // TODO: how to mergeXpp3Dom lists rather than override?
         // TODO: share this as some sort of assembler, implement a walk interface?
+        if ( recessive == null )
+        {
+            return;
+        }
+
         Xpp3Dom[] children = recessive.getChildren();
         for ( int i = 0; i < children.length; i++ )
         {