Fix update_user_info avatar logic in service_user

Signed-off-by: Asai Neko <sugar@sne.moe>

service/service_user/update_user_info.go

@@ -87,6 +87,8 @@ func (self *UserServiceImpl) UpdateUserInfo(payload *UserInfoPayload) (result *U
 	}
 
 	if payload.Data.Avatar != nil {
+		val := *payload.Data.Avatar
+		if val != "" {
 			_, err := url.ParseRequestURI(*payload.Data.Avatar)
 			if err != nil {
 				execption := new(exception.Builder).
@@ -108,6 +110,7 @@ func (self *UserServiceImpl) UpdateUserInfo(payload *UserInfoPayload) (result *U
 
 				return
 			}
+		}
 		updates["avatar"] = *payload.Data.Avatar
 	}