Check the file exists

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-1/plugins/trunk@114132 13f79535-47bb-0310-9956-ffa450edef68

plugin/plugin.jelly

@@ -230,10 +230,11 @@
   
   <!-- test a plugin -->
   <goal name="plugin:test">
-    <maven:maven
-      descriptor="${basedir}/src/plugin-test/project.xml"
-      goals="testPlugin"
-      ignoreFailures="false"
-      />
+    <u:available file="${basedir}/src/plugin-test/project.xml">
+      <maven:maven
+        descriptor="${basedir}/src/plugin-test/project.xml"
+        goals="testPlugin"
+        ignoreFailures="false" />
+    </u:available>
   </goal>
 </project>