fix(RouteRegistry): initialize RouteParams.params

Fix a bug caused by RouteRegistry.generate not initializing RouteParams.params to a StringMap

Closes angular#3755

Author: IAPark

modules/angular2/src/router/route_registry.ts

@@ -211,7 +211,7 @@ export class RouteRegistry {
       } else if (segment == '' || segment == '.' || segment == '..') {
         throw new BaseException(`"${segment}/" is only allowed at the beginning of a link DSL.`);
       }
-      let params = null;
+      let params = {};
       if (i + 1 < linkParams.length) {
         let nextSegment = linkParams[i + 1];
         if (isStringMap(nextSegment)) {

modules/angular2/test/router/route_registry_spec.ts

@@ -79,6 +79,13 @@ export function main() {
       expect(url).toEqual('first/one/second/two');
     });
 
+    it('should geneate params as an empty StringMap when no params are given', () => {
+      registry.config(RootHostCmp,
+                      new Route({path: '/test/...', component: DummyParentParamCmp, as: 'test'}));
+      var instruction = registry.generate(['test'], RootHostCmp);
+      expect(instruction.component.params).toEqual({});
+    });
+
     it('should generate URLs of loaded components after they are loaded',
        inject([AsyncTestCompleter], (async) => {
          registry.config(