fixed the backward compatibility stuff

core/src/main/java/jenkins/model/JenkinsLocationConfiguration.java

@@ -4,6 +4,7 @@ import hudson.Extension;
 import hudson.Util;
 import hudson.XmlFile;
 import hudson.util.FormValidation;
+import hudson.util.XStream2;
 import net.sf.json.JSONObject;
 import org.kohsuke.stapler.QueryParameter;
 import org.kohsuke.stapler.StaplerRequest;
@@ -29,17 +30,26 @@ public class JenkinsLocationConfiguration extends GlobalConfiguration {
     private String adminAddress;
     private String jenkinsUrl;
 
+    // just to suppress warnings
+    private transient String charset,useSsl;
+
     public static JenkinsLocationConfiguration get() {
         return GlobalConfiguration.all().get(JenkinsLocationConfiguration.class);
     }
 
+    public JenkinsLocationConfiguration() {
+        load();
+    }
+
     @Override
     public synchronized void load() {
         // for backward compatibility, if we don't have our own data yet, then
         // load from Mailer.
         XmlFile file = getConfigFile();
         if(!file.exists()) {
-            file = new XmlFile(new File(Jenkins.getInstance().getRootDir(),"hudson.tasks.Mailer.xml"));
+            XStream2 xs = new XStream2();
+            xs.addCompatibilityAlias("hudson.tasks.Mailer$DescriptorImpl",JenkinsLocationConfiguration.class);
+            file = new XmlFile(xs,new File(Jenkins.getInstance().getRootDir(),"hudson.tasks.Mailer.xml"));
             if (file.exists()) {
                 try {
                     file.unmarshal(this);