Fixed the form submission error when there's no Ant or Maven configured.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@11170 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/Hudson.java

@@ -1575,8 +1575,9 @@ public final class Hudson extends View implements ItemGroup<TopLevelItem>, Node,
     }
 
     private boolean configureDescriptor(StaplerRequest req, JSONObject json, Descriptor<?> d) throws FormException {
-        // collapse the structure to remain backward compatible with the JSON structure before 1.238
-        JSONObject js = json.getJSONObject(d.getJsonSafeClassName());
+        // collapse the structure to remain backward compatible with the JSON structure before 1.
+        String name = d.getJsonSafeClassName();
+        JSONObject js = json.has(name) ? json.getJSONObject(name) : new JSONObject(); // if it doesn't have the property, the method returns invalid null object.
         json.putAll(js);
         return d.configure(req, js);
     }