Work around jelly bug when null value is provided

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-1/plugins/trunk@113686 13f79535-47bb-0310-9956-ffa450edef68

java/plugin.jelly

@@ -122,13 +122,15 @@
 
   <goal name="java:jar-resources"
         description="Copy any resources that must be present in the deployed JAR file">
-        
+    <j:set var="build" value="${pom.build}"/>
+    <j:if test="${!empty(build)}">
       <j:if test="${!pom.build.resources.isEmpty()}">
         <resources:copy 
           resources="${pom.build.resources}"
           todir="${maven.build.dest}"
         />
       </j:if>
+    </j:if>
   </goal>
   
   <define:taglib uri="java">