Fix serialization issue when required object is empty (#337)

* Fix serialization issue when required object is empty

* Update constants

lib/serviceClient.ts

@@ -483,6 +483,10 @@ export function getOperationArgumentValueFromParameterPath(serviceClient: Servic
       serializer.serialize(parameterMapper, value, parameterPathString);
     }
   } else {
+    if (parameterMapper.required) {
+      value = {};
+    }
+
     for (const propertyName in parameterPath) {
       const propertyMapper: Mapper = (parameterMapper as CompositeMapper).type.modelProperties![propertyName];
       const propertyPath: ParameterPath = parameterPath[propertyName];

lib/util/constants.ts

@@ -8,7 +8,7 @@ export const Constants = {
    * @const
    * @type {string}
    */
-  msRestVersion: "1.8.0",
+  msRestVersion: "1.8.1",
 
   /**
    * Specifies HTTP.

package.json

@@ -5,7 +5,7 @@
     "email": "azsdkteam@microsoft.com",
     "url": "https://github.com/Azure/ms-rest-js"
   },
-  "version": "1.8.0",
+  "version": "1.8.1",
   "description": "Isomorphic client Runtime for Typescript/node.js/browser javascript client libraries generated using AutoRest",
   "tags": [
     "isomorphic",