Do not registerGadget more than once for an ID. Add tests for this.

renderjs.js

@@ -498,7 +498,10 @@ var RenderJs = (function () {
                     /*
                      * Register gadget
                      */
+                    if (RenderJs.GadgetIndex.getGadgetById(gadget.id) === undefined) {
+                      // register only if not already added
                       gadget_list.push(gadget);
+                    }
                 },
 
                 unregisterGadget: function (gadget) {

test/renderjs_test.js

@@ -62,12 +62,16 @@ function setupRenderJSTest(){
       dom = $("#qunit-fixture");
       deepEqual(["new"], RenderJs.GadgetIndex.getGadgetIdListFromDom(dom));
 
+      // try register gadget twice and check it's registered once only
+      RenderJs.GadgetIndex.registerGadget(RenderJs.GadgetIndex.getGadgetById("new"));
+
       // test unregister gadget
       equal(RenderJs.GadgetIndex.getGadgetList().length, 1);
       equal(RenderJs.GadgetIndex.getGadgetById("new"), RenderJs.GadgetIndex.getRootGadget());
       RenderJs.GadgetIndex.unregisterGadget(RenderJs.GadgetIndex.getGadgetById("new"));
       equal(RenderJs.GadgetIndex.getGadgetList().length, 0); 
     });
+
    });
 
   module("GadgetObject");