fix crash after adding or deleting a friend

When a request is made with no callback argument data,
there will be a segfault.

One origin of the request is:
lwqq_info_allow_and_add() at the line:
return req->do_request_async(req,1,post,_C_(2p_i,info_commom_back,req,NULL));
Merge pull request #157 from lawm/dev

fix crash after adding or deleting a friend by lawn