check request.status in httpsync.js to prevent throwing errors when undefined

lib/httpsync.js

@@ -37,8 +37,10 @@ HttpSyncProvider.prototype.send = function (payload) {
     request.open('POST', this.host, false);
     request.send(JSON.stringify(payload));
 
-    // check request.status
     var result = request.responseText;
+    // check request.status
+    if(request.status !== 200)
+        return;
     return JSON.parse(result);
 };