fix #1354 check xmlrpcurl returned by getusersblogs

fix #1354 check xmlrpcurl returned by getusersblogs

Display this specific error:
![screencap-2014-05-19t16-02-35 0800](https://cloud.githubusercontent.com/assets/40213/3011538/fc1b5854-df2b-11e3-8221-a96d6c7774cd.png)