add migrate wx_user function

go/gopath/src/fohow.com/apps/controllers/user_controller/user_controller.go

@@ -459,6 +459,9 @@ func (self *UserController) SysUserBind() {
 	}
 
 	sysWxUser := user_model.GetWxUserByUserNo(userNo)
+	if sysWxUser == nil {
+		self.ReturnError(403, apps.NoExist, "", nil)
+	}
 	//同步会员资料--原会员迁移至新会员(除ID，invite_id之外)
 	sysWxUser.UserId = wxUser.UserId
 	sysWxUser.MpOpenid = wxUser.MpOpenid