[FIXED JENKINS-16928] Don't create mojo config key if it didn't exist.

Fixes: Maven2 builds with non-standard test mojos failed.

changelog.html

@@ -61,6 +61,9 @@ Upcoming changes</a>
   <li class=bug>
     “Build” from job context menu produced a confusing warning page.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-16844">issue 16844</a>)
+  <li class=bug>
+    Maven2 builds with non-standard test plugins failed.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-16928">issue 16928</a>)
 </ul>
 </div><!--=TRUNK-END=-->
 

maven-plugin/src/main/java/hudson/maven/reporters/SurefireArchiver.java

@@ -93,7 +93,7 @@ public class SurefireArchiver extends TestFailureDetector {
             // Many test plugins have - as surefire - a configuration key 'testFailureIgnore' which defaults to
             // ${maven.test.failure.ignore}, so just try that one and change value to true,
             // if it's still at that default:
-            XmlPlexusConfiguration c = (XmlPlexusConfiguration) mojo.configuration.getChild("testFailureIgnore");
+            XmlPlexusConfiguration c = (XmlPlexusConfiguration) mojo.configuration.getChild("testFailureIgnore",false);
             if(c!=null && c.getValue() != null && c.getValue().equals("${maven.test.failure.ignore}") && System.getProperty("maven.test.failure.ignore")==null) {
                 if (build.getMavenBuildInformation().isMaven3OrLater()) {
                     String fieldName = "testFailureIgnore";